VOL. 13, NO. 3 REVIEWS OF GEOPHYSICS AND SPACE PHYSICS JULY 1975

Soil Water C. R. Amerman,' A. Klute,* R. W. Skagg~ ,~ and R. E. Smith4

Recent advances in developing methods to solve the plication in evaluating the worth of both simple and com- equations governing combined saturated-unsaturated plex models for predicting water movement in the field. flow in two and three dimensions [Freeze, 1971; Stephenson Research is continuing toward developing, testing, and and ~reeze, 19741 have focused attention on the need to refining methods for calculating the hydraulic conduc- determine effective field values of the hydraulic properties tivity function from the soil characteristic. ~~~k~~~ of the soil- l3ecause of natural variation from point to [I9721 compared prediction methods of Marshall [I9581 point, hydraulic properties for field-Size Units are difficult and of Millington and Quirk [1959] for four soils. He found to characterize. A detailed field study was conducted by that when a factor at saturation was used, hy- Nielsen et al. [I9731 to determine the field variability of draulic conductivity could be calculated within the the hydraulic properties of the soil and to test various field limits of error of measurement. Comparison with field methods of measuring these properties. They conchded measurements for one soil showed that field hydraulic that even seemingly uniform land areas manifest large conductivity functions could be calculated reasonably by variations in hydraulic conductivity. For a given point, these a conc~usion also drawn by Nielsen et al. methods for measuring the soil hydraulic properties will [I9731 in the study discussed above. Roulier et al. [I9721 give values that are more accurate than those required to were less successful in using these to characterize an entire field because of the heterogeneity calculate the hydraulic conductivities of field soils but of the soil. Thus the ability to make predictions over a found that the agreement between measured and calcu- large area from soil properties determined a t one location lated values was satisfactory when the matching factor can range from good to unsatisfactory, depending on the was determined near the midpoint of the suction range of prediction parameter of interest. Because of field varia- interest. Bruce [I9721 found prediction methods worked tion in the hydraulic properties of the soil, simplified reasonably well for coarse-grained soils but were less methods for calculating soil water flux and water contents satisfactory for fine-textwed soils with a wide pore-size during redistribution were f ~ u n d to be satisfactory when range. Campbell [I9741 used the same basic approach as they were compared with more detailed numerical Millington and Quirk but obtained a closed form expres- methods and with field ~ ~ ~ ~ s u r e m e n t s - Furthermore, sion for the conductivity function by assuming an empiri- when field variability is considered, simplified methods for cal equation for the soil water characteristic. His methods measuring hydraulic conductivity or soil water diffusivit~ worked well for five soils tested when a matching factor are sufficiently accurate for characterizing field condi- was wed a t satwation. Sinelair et [1974] predicted hy- tions. The results of this study will have continued ap- draulic conductivities with a Burdine-type equation and

compared them with measured values for seven soils. 'USDA, Agricultural Research Service, North Central Region, Skaggs et aL [I9731 presented an approximate method for

Columbia, Missouri 65201. determining the hydraulic conductivity function from the WSDA, Agricultural Research Service, Western Region, Fort

Collins. Colorado 80521. Also ~ t h Department of Aaronomy, soil water characteristic and a measured infiltration rate- - .

Colorado State University, Fort Collins, &lorado 80521. time relationship. Qepartment of Biological and Agricultural Engineering, North Thermal and osmotic effects on soil water movement Carolina State University, Raleigh, North Carolina 27607. 4USDA, AgriculturaI Kesearch WBstern Region, Tuc- are being analyzed with the methods of irreversible ther-

son, Arizona 85705. modynamics [Kay and Groenevelt, 1974; Groenevelt and Copyright a' 1975 by the American Geophysical Union. Kay, 1974; Joshua and de Jong, 1973; Banin and Low,

19711 or by more mechanistic approaches [Kemper et al., 1972; Harlan, 19731.

Considerable progress has been made by Groenevelt and his co-workers in exploiting the irreversible ther- modynamic approach. In their analysis they have dis- tinguished between the microscopic continuum and macroscopic continuum points of view of a porous medium. Many who have attempted to apply the concepts of ir- reversible thermodynamics have not carefully recognized this distinction and have been led to incorrect formula- tions and interpretations of the transport equations. The review by Groeqeuelt and Bolt [I9691 and two recent papers [Kay and Groenevelt, 1974; Groenevelt and Kay, 19741 report perhaps the best attempt that has been made to date in developing transport equations via irreversible thermodynamic concepts. In the latter two papers the in- teraction of water and heat transport in frozen and unfrozen soils is considered. Coupling between the two transports is related to the heat of vaporization, the heat of fusion, and the partial specific heat of wetting of the soil water. (It appears that the term 'coupling' is used to refer to two kinds of phenomena: (1) the contribution to the flux of water due to a thermal or solute gradient (and vice ver- sa) and (2) the effect of the thermal or solute regime upon the transport coefficients for water movement. In this dis- cussion, only the first kind of phenomena is considered.) An experimental study of the coefficients for coupled flow of heat and moisture was reported by Jury and Miller [19741. Results were analyzed within the framework of the irreversible thermodynamic approach and also with the concepts of the theory of Philip and de Vries [1957]. The coupling coefficient for water flow due to a temperature gradient was found to be much larger than that predicted by the surface tension-based model of Philip and de Vries.

Krupp et al. [I9721 combined the miscible displacement equation and Gouy double-layer theory to develop a model for salt flow through a soil column during miscible dis- placement. Bresler [1973a, bl developed a numerical simulation based on linking the diffusion-convection equa- tion with a Darcy-type water flow equation for isothermal, unsaturated porous media flow. The model accounts for physicochemical interactions between solutes and the soil matrix by considering coupling effects and the mecha- nisms of convection, ionic diffusion, mechanical disper- sion, and anion exclusion. Bresler and Laufer [I9741 tested the Bresler model in the laboratory and numerically. Numerical tests indicated that osmotic gradients and anion exclusion effects are of minor importance in the up- per parts of soils subjected to infiltration, redistribution, and evaporation.

Building on the work of McLaren [ I9694 b, 1970, 19711 and McLaren and Skujins [19631, Starr et al. (19741 and Misra et al. [1974a, b, cl developed transport equations of the movement of various nitrogen species during leaching in unsaturated soils. The models simulate simultaneous nitrification and denitrification and stiochemetrically relate the transport and retention of nitrogen species in the gaseous phase to those in the liquid phase.

Cary and Mayland [I9721 investigated salt and water movement in unsaturated frozen soil. Flux equations for water and salt, which included coupling coefficients for both flows, were proposed. It was emphasized that frozen unsaturated soil should not be considered as a static

system. Not all the soil water freezes a t temperatures com- monly experienced in the field. Liquid films remain be- tween the solid and ice phases, between the solid and air phases, and between the ice and air phases. Soluble salts are forced into these films. Liquid water and vapor tend to move from warmer to cooler areas. Much of the flow is in the liquid films. Thus solutes will also be carried from warmer to cooler regions.

Joshua and de Jong [I9731 measured the coupling coeffi- cients between heat and moisture flow. The results were analyzed by using the theoretical framework of irreversi- ble thermodynamics and the Philip-de Vries theory. The agreement between the thermodynamic theory and the Philip-de Vries theory was satisfactory between 0.3- and 15-bar soil water suction. At suctions below 0.1 bar the Philip-de Vries theory predicted more coupling than was observed. Future work on coupled flows should consist of careful experiments on a variety of soil materials under a range of conditions to test the validity of the transport equations that have been proposed.

A more mechanistic approach to the analysis of osmotic flow in clays and soils has been taken by Kemper et al. [1972]. A theory was advanced to explain the nature and mechanism of osmotic flow in such media. According to the theory, solution concentration differences in in- compressible media are translated into a hydraulic pressure gradient which moves the solution to the high- concentration side. Similar concentration differences in compressible media cause electro-osmotic movement of solution to the high-concentration side. The concepts out- lined are relatively untested, and further investigation is necessary.

The effect of temperature on the pressure head, water content, and conductivity relationships of two silt loam soils was studied by Har~dasan and Jensen (19721. The temperature dependence of the pressure head-water con- tent relation could not be explained on the basis of changes in surface tension of air-water interfaces. The ob- served increase in hydraulic conductivity a t a given water content due to an increase in temperature was almost en- tirely accounted for by the decrease in viscosity of water.

The effect of solutes on the hydraulic properties of various materials has been examined by several investiga- tors. Elgabaly and Elghamry [I9701 measured hydraulic conductivity of kaolite as affected by adsorbed cations; Naghshineh-Pour et al. [I9701 studied the hydraulic con- ductivity of several soils in relation to electrolyte composi- tion; and Shainberg and Caiserman [I9711 and Shainberg et a1 [I9711 studied the hydraulic conductivity and swell- ing pressure of NaICa montmorillonite systems. The hy- draulic conductivity of axially loaded soils during cyclic calcium-sodium exchanges was measured by Waldron and Constantin [19701. All these results shed partial light on the kinds of effects to be found, but a systematic treat- ment and coherent account of the effects of solutes on hy- draulic properties are still lacking. In view of the recent increased interest in modeling of solute and water move- ment there is added motivation for obtaining better knowledge of these effects.

A very thorough experimental study of the soil water, chloride, and heat transport in the upper 10 cm of a bare field soil has been conducted by Jackson and his associ- ates a t Tempe, Arizona [Jackson et al., 1973; Nakayama at

al., 19731. The time and depth patterns of soil water flux in this zone of the soil profile clearly displayed the dynamic nature of the flux. The applicability of theories of coupled heat, salt, and water flow to this situation is being ex- amined.

Carter et al. 119711, in a noteworthy and monumental effort, studied the effect of irrigation return flow from an 82,030-ha (202,700-acre) tract into the Snake River. They sampled water diverted from the river and sampled return flow a t many sites. They found that about 50% of diverted water was returned, that i t was higher in nitrates and soluble salts than when it was diverted, but lower in PO4- P. About 30% of the PO4-P present in diverted water was returned. Applied fertilizer apparently did not leach. Sub- surface drainage water contained about twice the con- centration of soluble salts originally present in the irriga- tion water. NO,-N concentrations increased several fold (to 3.24 ppm) in subsurface drainage water but were con- siderably below drinking water standards (10 ppm).

In most analyses of water flow in unsaturated soils it has been implicitly assumed that solutions of the flow equation are stable, i.e., that small perturbations in flow patterns will tend to disappear. With this assumption it is possible to describe infiltration by numerical and analyti- cal techniques of solution of the soil water flow equation. The water content profile in the transition zone between the wet and dry regions depends on the hydraulic conduc- tivity and water retention characteristics of the soil. Various experimental observations [Hill and Parlunge, 1972; Smith, 1967; Crosby et al., 1968; Tabuchi, 19611 and theoretical considerations [Saffman and Taylor, 1958; Wooding, 19711 show that the stability assumption is not always justified. When infiltration occurs in a layered soil in which the upper layer is finer and less conductive than the coarser layer beneath, the wetting front becomes unstable and breaks into narrow wetting columns or 'fingers.'

The Green and Ampt model of infiltration \Green and Ampt, 19111 has recently been employed by Raats 11973~1 to develop criteria for stability of the wetting front in uniform and nonuniform soils. Instability due to an in- crease of air pressure ahead of the wetting front was ob- served by Peck [I9651 and is predicted by the theory developed by Raats. Instability is also indicated by Raats' theory during infiltration of nonponding rainfall into soils with a narrow range of pore sizes and during ponded and nonponded infiltration into soils in which the conductivity increases with depth.

The stability of the flow is of fundamental importance in problems involving recharge to the water table and move- ment of pollutants. If the front is unstable, one-dimen- sional solution of the water flow equation cannot be used to predict the percolation. Stability considerations should play a large role in soil water flow studies in the future.

In the period since 1970, investigators have continued to take advantage of the increasing power of the digital com- puter to study flow of water in porous media. Recent studies have advanced knowledge of flow processes by studying increasingly less simplified systems. Two phenomena receiving increasing attention are the inter- relation of air flow and water flow and flow in a swelling medium.

Much work on describing two-phase (air and water) flow

systems has taken place a t Colorado State University. Concentrating on the infiltration process, Brustkern I19701 employed a Buckley-Leveritt approximation from oil technology to approximate the effect of air on infiltra- tion. The four equations (flow of air and water and conser- vation of mass for air and water) were programed for finite difference solution by Phuc 1Phuc and Morel- Seytoux, 19721. His results agreed in principle with those of Brustkern, indicating significant reduction in infiltra- tion capacity under conditions of limited vertical distance to an impermeable boundary. A characteristic drop and rise in infiltration rate when air counterflow occurs (exits a t the surface) was also shown [Morel-Seyfouz, 19731. A different mathematical approach was used by Noblanc and Morel-Seyioux [19721, in which the flow process was studied by considering zones in which certain simplifying assumptions could be made without major error. The resulting procedure allowed numerical solution involving an integral equation and matching solutions a t the solu- tion zone interface.

Excellent experimental demonstration of the nature of the effect of air flow on infiltrating liquid flow was given by McWhorter 119711. Analytical solution for horizontal flow and approximate solutions for vertical flow under several boundary conditions were also developed. The ex- perimental work included a careful study of infiltration into various closed column lengths of sand. Shorter col- umns exhibited the theoretically predicted early drop and recovery of infiltration rate.

It seems fair to say that characterizing hydrodynamics of two-phase porous media flow involves (1) obtaining in- formation on those conditions in which the gas phase can- not be neglected and (2) obtaining efficient methods to calculate water movement, almost always the item of practical interest in those cases. The physics of the role of two-phase flow are rather easily described in partial differential terms. It is the recognition of sensitivity, rela- tive magnitude of effects, and efficiency of methods of calculation that now concern the investigators. From the progress to date, i t appears that continuing study will bet- ter show (1) which soil conditions will necessitate two- phase calculations for infiltration and drainage computa- tions, (2) those assumptions about the properties of the soil and soil air to which calculation of time and extent of air counterflow are most sensitive, and (3) mathematical approximations and simplifications for modifying older in- filtration rate formulas to account for air effects.

Progress has been made in characterizing the effect of a swelling soil medium on its pattern of imbibition of water [Philip, 19716, 1972; Smiles, 1974; Groenevelt and Bolt, 1972; Sposi~o, 19731. Again the theoretical description of water movement and distribution in a soil whose swelling nature is well defined by a relation of void ratio, porosity, and pressure can easily be laid out in partial differential relations. Useful in this respect is the use of a material coordinate system which expands with the swelling media. Results to date have demonstrated that swelling acts counter to gravitational effects, thus reducing vertical in- filtration to a phenomenon more resembling capillary rise. The key to use of results to date is, of course, the ability to characterize the swelling relations of the soil. Problems of complexly stratified swelling systems are yet to be dealt with.

In the field, soil water flow occurs in a cyclic manner with periods of drainage, redistribution, and evaporation alternating with periods of wetting. The flow involves the phenomenon of hysteresis. The boundary conditions are time dependent. Analytical methods for solution of the water flow equation under these circumstances are not available. although certain bounds and limits on the behavior of the solution can be developed [Philip, 19731. Numerical solution techniques offer the possibility of ex- amination of some of the detailed flow behavior of flow systems with time-dependent boundary conditions. Soil water pressure head and the development of the profiles of water content were examined by a numerical solution scheme for the Richards equation of soil water flow I Klule and Heermann, 19741. Hysteresis in the water content- pressure head relation was incorporated into the solution procedure. An arbitrary sinusoidal variation of pressure head a t the soil surface was imposed. The wave forms of water content, pressure head, and flux exhibited a progressive increase in phase lag and decrease in amplitude with depth. The highly nonlinear soil water flow system introduced a high degree of harmonic distor- tion into the response of the system to the applied bound- ary condition. Further work along these lines should (1 ) examine the behavior of the profiles in a range of soil materials, ( 2 ) make use of better methods of representing and incorporating hysteresis into the solution scheme, (3) utilize a periodic boundary condition involving evapora- tion, and ( 4 ) investigate the possibilities (if any) of analytic approaches to problems of this kind.

One of the significant developments in the soil water research of the past 4 yr was the application of the in- tegral method to the solution of the soil water equation. This is a quasi-analytic method in that solution by suc- cessive approximations is necessary. The number of ap- proximations required is few, however. Parlange 11971a, b, c, 1972a, b, c, d, e, 19731 and Parlange and Aylor 119721 ap- plied the method to a variety of flow situations including one-, two-, and three-dimensional adsorption and infiltra- tion under both steady and transient conditions.

Knight and Philip (19731, however, found that the sec- ond- and higher-order approximations in Parlange's method do not satisfy continuity requirements. As a conse- quence, higher-order approximations oscillate with in- creasing amplitude about the exact solution. They con- clude that the utility of Parlange's method is that of the first approximation and that the method cannot be applied

-, A., md P. I. lor. Simlt.ruoru tno .pert of ultu d ult through c h y s : 2. Study-.Ute d i s u f b u t i o a of p r ~ a n a .ad appli- u b i l i t y of irraurrsibla ~ r m d ~ 8 . S o i l Sc i . . l l 2 , 69-80, 1971.

Bres lm, W, S i l l l l l a e a u transport of s o l u t ~ md u t c r d c r m a a i a t t u a r u r a t e d f l a conditions, Water Relour. Pea. 9(4). 975-986, 1973a.

Bresler. B.hd. M o n e a c l w i o n md c o u p l w e f f . c u i n m ~ t a s d y u s l u p o r t through unsaturated .oils: I. Th.ory, S o i l Sci. Sac. *Irr. Pme.. 37(5), 663-669, 1973b.

B r u l e r , K., md A. Laufu. Anion -1wiom d coupling affmcts i n m- a t e d ~ transport through unaarunted s o i l s : 11. L.boracolq a d r*nrricd txp.ri..nta. S a i l Sc i . Soc. dYT. Proe.. 38(2). W-218. 1974.

Bmec, P. I., Eydraulic conductivity nraltutien of the d prof i le from s o i l m t e r retention r e l a t i o m . S o i l Sc i . Soc. h r . Proc.. 3614). 355-561. 1972.

Bwtkam. R. L.. md 8. J . mrsl-Saytour, Amlyrical t r e a o m t of NO-

p h u a inf i l trat ion . J . EPdrull. Div.. Aner. Scc. Civ i l W.. 9 6 ( m l 2 ) , 2535-2548, 1970.

Cupbel l , C. S . , A simple method for determining unuhlr.ced coniuctivity frol v i s t u r e retention data, Soil Sc i . . 117(6), 3ll-314. 1974.

to the two- and three-dimensional cases unless they are radially symmetrical.

For the one-dimensional absorption case, Philip and Knight 119741 developed a quasi-analytical solution simi- lar to Parlange's but preserving continuity in higher-order approximations. The next few years will probably see con- tinuing development of these methods.

An analytical, as compared with a numerical, solution of the flow equation for a particular application is quite valuable in that it yields a general description of the flow situation of interest. That is, one may study with relative ease the effects of making changes in hydraulic boundary condition and of changing dimensions of the flow regions. A number of analytical solutions have appeared recently. For example, Raats 11970, 1971, 19721, Philip 1197la, 19721, and Zachmann and Thomas 119731 have developed such solutions for steady seepage from point and line sources, cavities, and basins. Warrick 119741 and Lomen and Warrick 11974 1 have contributed solutions for unsteady flows from point and line sources. These solu- tions yield matric flux potential, stream functions, and total hydraulic head distributions for flows of significance to furrow and subsurface irrigation. These solutions also provide a basis for the discussion of leaching under irriga- tion.

Warrick 11970j, Morin and Warrzck 119731, Warrick and Lomen 119741, and Selim and Kirkham 11972a, bl have ap- proached hillside seepage from an analytical standpoint. Under saturated conditions there may be several alternat- ing zones of infiltration and exfiltration from the top to the bottom of a slope.

R a t s (1973bJ has reported on steady upward and down- ward flows. He demonstrates a maximum upward flux for a given depth of water table and also describes the two types of downward flow that can occur in the zone im- mediately above an interface between two soil layers.

Analytical models cannot be developed for all porous media flow situations, and so it is often necessary to rely on numerical methods. Recent years have seen notewor- thy progress in the application of the finite element method to porous media flow problems IGuymon et al., 1970; Guymon, 1972; Cheng and Li, 1973; Rubin and James, 1973; Neuman, 19731.

Acknowledgment. This paper is the report of the Committee on Soil Water, American Geophysical Union.

Cuter . D. 1.. J. A. Bondurau, md C. W. Rabbina. Y.cer-soluble m3- IIitmgRII, PO -phospbow. awl tota l u l t b a h c a s on a U r g e i r r i y t i o n &act, S o i l Sei. Soc. -1. Roc.. 35(2), 331-335, 1971.

C.rg. J . W.. and 8. I. Lllylud, Sal t .nd m t u rmnt i n u ~ ~ a t u ~ a t e d fmren .oil, S o i l Sei. Sac. &a. Roe.. 36(4). 549-555. 1972.

Chew, sllpb Ta-Shu~. and Chih-Yen Li, On t b ~ l u t i e n of transient frecaurface flow p r o b l a i n porous udi. by chc f i n i t e el-t rthcd, J. Bpdml.. 20(1), 49-63, 1973.

Cmsby. J. W.. D. L. J o b t m . C. 8 . a d P L Panton lligratioa of p l l u t a n t a i n a ~ i . l o u ~ s h emir-;. Uctar -9.. 5. 1095-1113, 1968.

S I W ~ Y , n. n., .ad v. r. s l g m , urter pe~-t.uity a d s t a b i l i t y oi L.ol in l te a p t m a s inf1~01c.d b~ adsorbed u c i o n rat io , Soil Sei . . 110. 107-110, 1970.

kcan, W. 8.. and C. A. h p t , Studha in physics. I. The £1- o f air sad r . u r throu* s o i l s , J. &I. Sci . . 4, 1-2.(, 1 9 l l .

G-elt. P. 8 . . and C. 8. Bolt, k n - q u i l i b r h t h e d g a m i e s of the MIL m t e r apt(. , J. 3358-388. 1969.

Gromevdt . P. H., and C. 8. Bolt, U a t a re tont ion in r o i l . S o i l Sci.. m, 238-245, 1972.

Cr-elc, P. 8.. md 8. D. R.7. On the in terac t ion of water md but cmanaport in f rosan a d vafmzan . o i l s . 11. The l iquid p k e , Soil ki. Soc. dur. Roc. . 38(3), 400-404, 1974.

Cuy.on, C. L., @at* on the f i n i t e el-t so lu t ion of the diffusion- convection equation, Wamr Usour. Bss.. 8(5). 1357-1.360, 1972.

Cuyuon, C. L., V. R. Scott. rrd L. I. kr-nn, A penera1 n l~(c ic .1 ~Olut iOn Of the t d - i o d d i f f u s i o n - ~ 0 m ) e ~ t i o n mqrution by the f i n i t e dement method, Wawr h o u r . Res.. 6(6), 1611-1617, 1970.

&ria-, n.. md a. D. J a m , Effect of t-amre on pressure h u d - v a t u contsn t ralrrti-hip md conductivity of NO r o i l s . S o i l Sci. Soc. Amm. Roc. . 36(5), 703-708. 1972.

m r l a n , 1. L., bnr lys is of coupled h u t - f l u i d t r a m p o r t i n p a r t i a l l y froran r o i l . Water Resour. h., 9 0 ) . 1314-1323. 1973.

Hi l l , D. E. , and J. Y. Parlange, UattLng f ront i n s t a b i l i t y i n layered wm. S o i l Sci. Soc. ha. PIOC., 36(5). 697-702. 1972.

JlcLwn, I. D., On the u l c u h t i o n of hydraulic conductivity, u. Soc. a. Proc., 36(2), 380-382. 1972.

Jackson. R. D., B. A. m, R. J . R q b t o , a d P. 5. m y a m , Diurnal coil-ter evaporation: Timedepth-flux pa t te rns , M. Soc. &ex. Roc.. 37(4). 505-509, 1973.

l o s h u , U. D., and E. da J a q . Soi l l o i r t u r e n n v u n t under temperatucr gradients, Un. J. S o i l Sc i . , 53, 49-57, 1973.

Jury. W. A., a d E. E. Will-r. !4usuresenc of the transport coef f ie ian ts for coupled f l w of heat snd mLtNn i n a d. Soi l Sci. 5%. Amr. Prof.. 38(4). 551-557, 1974.

b y . 8. D.. .ad P. H. Gcoenevalt. 00 the in terac t ion of -tar and h u t t r u u p a r t i n tr0r.a a d u n f m u n sotla. I. hslc theory: Ih. vapor phew. S o i l S-S. See. W. P m . . 36(3), 395-400, 1974.

Y..per, U. D., I. Sbinberg , and J. P. puirk, Swelling pressures e l e c t r i c p o t . n ~ s , ion c o a c e m t r a t h : mir m l s in .nd o m t i c f l w throvpb clays. S o i l Sci. Soc. h r . Pmc.. 36(2), 229-236, 1972.

U u t e , A.. and D. P. Fleermum. S o i l v r t a p r o f i l e dev.1-nt under a periodic boundary condition. oil ki.. n, 265-271, 1974.

Knisht, J. H.. md J. R. Phi l ip On solving cha m a t u r a t e d f lou e q u t i o n : 2. Cr i t ique of Par-a'a L t h o d . S o i l Sci.. 116. 407416, 1973.

m p , H. K., J . U. Bigaar, and D. I(. Nielam, Relative f l w ra t - of sllt .nd water i n s o i l , S o i l Sci. Sac. Aur. Proe., 36(3), 412-417. 1972.

Loun, D. 0.. and A. W. Warrick, T W e p e d e n t l inear ized M i l t r a t i o n . 11. Line sourus, S o i l Sci. Soc. h r . Pme.. 38(4), 568-572, 1974:

Wrahal l . T. J., A r e l a t i o n b e h n c n pameabi l i ty and s i z e d is t r ibut ion of pores, J: Soi l Sci.. 9. 1-8. 1958.

kLusn, A. D., S t u d y s t a t e .Mi- of n i t r i f i c a t i o n in coi l : Theoretical conaideraciolu, S o i l Sci. Soc. ikcr . Roc. 33(2), 273-275, 19698.

n u r r e n , A. D., a i t r i f i c a t i o n in M i l : S y a t a app-hh a atosdy a ta te . S o i l Sc i . Soc. Amr. Roc.. 33(4), 551-556, 1969b.

Warm, A. D.. Tenporal and v e c m r i p l r ~ c t i o l u of nitrogen i n s o i l : A review, Can. J. S o i l Sci.. 50. 97-109, 1970.

khrm, A. D., Kinetics of n i t r i f i c a t i o n i n s o i l growth of n i t r i f i r r s , S o i l Sci. Soc. her. Proc.. 35(1), 91-95. 1971.

IkLaren. A. D., and J. J. S h j i ~ . N i t r i f i c a t i o n by n i t robacter q i l i a on sur faces and i n a o i l v i t h respect t o h y d q e n ion c o m ~ n t r a t i o n , Cm J. Hicrobiol.. 9, 729-731, 1963.

* k r t e r , David B., I n f i l t r a t i o n affected by f l w of .k, 43 pp H~droloa , b a r s @a. 49, Colorado S t a t e University, ~ t . ~ o i i ~ ~ . Calo.. 1971.

Nillingcon. R. J . , a d J. P. Quirk, P e m a b i l i t y of porous media, Nature.. 183, 367-388. 1959.

&ra. C. , D. R. Nie1s.n. and J. U. B i m u , N i t r o p a t r a n s f o m t i o n s i n s o i l during leaching: I. T h o o r a t i d comiders t ioru . S o i l Sc i . Sot. Mr. Proc.. 38(2). 289-293. 1974..

Niara, C., D. 9. Mialaan, .ad J. U. Bi&wr, Hitm8.n tranaf-tiolu in s o i l dur- leaching: 11. S t u d y s t a t e n i t r i f i u t i o n end n i t r a t a reduction. S o i l Sci. Soc. h e r . Proc.. 38(2), 294-299. 1974b.

Msra, C., D. U. Uielsur, and J. W. B i g y r , Nitrogen t r ~ f o r u t i o r u in w i l d u r i q leaching: 111. Nit ra te r d u c t i o n i n c o i l wlunna. Sei. Soc. h r . Roc.. 38(2), 340-304, 1 9 7 4 ~ .

Ibral-Saytour. 8. J., Tw-phue fl- in por- d i a , & 119-202. A c a d d c RUS. Mu York, 1973.

k r i n , C. C. A.. and A. 9. Warxick, S t u d y - s u t r .**pale in a hillrid.. Soi l Sci. Soc. A u r . Roc., 3 7 0 ) . 346351, 1973.

w h i n e h - P a u , B., G. Kme., a d C. Carson. The e f t s t of electrolyte c a p o r i t i o n on hydraulic conductivity of c e r t a i n T . u r s o i l s , Sci.. 110. 124-127, 1970.

I3akay.1.. P. S., R. D. J.eL.on, B. A. K W , md R. J . w t o , Diurnal coil-uatar nnpora t ion: Chloride w v w t .Id a c d t i o n war the s o i l surface. S o i l Sci. Soc. k. P-.. 37f4). 509-513, 1973.

-n, S. P.. Saturated-&maturated s..p.se by finiu J, Hmtraul. Div.. bur. Soc. C i v i l Bar.. 9 9 W 1 2 ) . 2233-2250. 1973.

Nieleen, D. R., J. w. Bi%g8rr, .Id K. T. Erh. Spat ia l v a r i a b i l i t y of field-musured coil-tar propcrries, Hilnardia, 42(7), 215-260, 1973.

W b l n c . N a i n , and H. J. norel-S.ytnu, Pertur&tion analys is of two- phe- i n f i l t r a t i o n , J. mdrd. Div., her. Soc. C i v i l &.. ~ m 9 ) . 1527-lS41. 1972.

P a r 1 - w . J., Thwry d va--t in m i l e : 1. MW- rb-rption, S o i l Sci.. U1. 134-U7, 197la.

P e r h q c , J., Theory of w a t e r - m r u n t i n .ails; 2. -IOD.~ i n f i l t r a t i o n , 17111.174, 1971b.

P a r w e , J., rn-ry of weter-mw-~t in soi lq : 3. rvo .~d thru d*iod absorption, SU-31313-317, 1 9 7 1 ~ .

-

Parlmg., J., Theory of w o t e r - x w u n t i n r o i l s : 4. hro end thru dirursio-1 s t u d y i n f i l t r a t i o n , S o i l wi.. 113, 96-101, 3972..

Parlenpe, J.. Theory of rater-t in s o i l s : 5. U l u t ~ d y i n f i l t r r t i o n f r m spherical e w i t i u . S o i l Sd., 113, 156161. 197%.

h r l n a g e , J., Theory of v r t u - m v a a n c i n soils: 6. Effect of ~ t s r depth over Soil*, Soi l Sci. , U 3 , 308-312, 1 9 7 2 ~ .

Parlange. J., 'theory of water -vunt in soi l s : 7. lhltidhmsioml cavi t ies udder pressme, Soi l Sci. . U, 379-382, 19726.

P u l a w . J., Theory of enter-acne i n w i l e : 8. O n a - d m h l i n f i l t r a t i o n v i t h canstant f lux a t tho surf-, S o i l Sci.. 114. 1-4. 1972..

Par lawe, J . . Thwry of m t u m0v-t in so*: 10. h i t ies wlth e o l u u n r flux, S o i l Sci., U6, 1-7, 1973.

Par*, J.. md D. Aylor, Theory of v r t e r -t i n wib: 9. l b ~YUMICS of capi l la ry ri.., S o i l Sei., U 4 , 79-81, 1972.

Peck, A. J . , Uoisture p r o f i l c d d - t and a i r c o l p r u u i o n dur* ra t - u p u L . by M a d p o w b o d i u r 3. V m r t i d c o l w , a Sci.. 104. 44-51. 1965.

Philip, J. R., bad t h r r on K u d y i n f i l t r a t i o n frm aucfaca M e u , v i t h applicatLon t o point rrd l i o c sarrc-, S o i l Sci. Soc. W. Roc.. 35(6), 867-871, 197la.

Phi l ip , J. 8.. tfgdmlop). of mil- s o i l s , S a l i n i m .nd Watu V u , pp. 95-107, d. by T. T d a m ad J. R. P h i l i p . )*llillm, loodon. 1971b.

Philip. J . H., S t u d y i n f i l t r a t i o n f m b u r i d , surf.c., md p u c w paint a d l i r u s o v r c u in h e t a ~ s r ~ u w .oils: I. u y s i . , Soil Sci. Soe. her . Proc.. 36(2). 268-273, 1972.

Philip, J . 8.. Periodic m n - l i n u r diffusion: An i n t e g r a l r e l a t i o n and its p b y a i d consaqwmcu. A w l . J. Ph~s . . 26, 5l3-519, 1973.

Phi l ip , J. B.. Md D. A. de V r i u , m i s t u r e r r v u n t i. p o w ntechls under temperature gradients. Trans. drr . k h y s . W o n . 38, 222- 232, 1957.

Phi l ip , J . , and J. h i p b t . On w l v i q the uqsatwatad flow . g u t i o n : 3, Nm q W ~ i 4 ~ l y t i & technique, S o i l Sci.. 117, 1-13, 1974.

Phuc, L. V., .ad 8. J. Word-Seytm, Effect of s o i l a i r r m n t .ad eorpress ib i l i ty on i n f i l t r a t i o n r a t e s , S o i l Sci. Sac. h r . Pmc.. 36(2), 237-241, 1972. -

B u t s , P. A. C.. Steady i n f i l m t i o n f r a l i n e sources and f-, Soil Sci. Soc. Ancr. Proc., 34(5), 709-714, 1970.

Buts, P. A. C., S t u d y i n f i l t r a t i o n f r m poin t wurces , cavities, .nd basins, S o i l Sci. be. dur. Roc., 35(5)., 689-694, 1971.

Paats. P. A. C.. Steady i n f i l t r a t i o n fm w u r c u a t a r b i t r a r y depth, Soi l Sci. Soc. d. Roc.. 36(3). 399-4Q1, 1972.

Buts. P. A. C., m u t a b l e wetting f ronts in usifom rrd lrounif011 m i l s , S o i l Sci. Soc. bur. Pmc.. 37(5), 681-685, 1973..

Bsst8. P.. steady upvrrd a& donuard flows in a c l a s s of umatura ted s o i l s , Soi l Sci. , 115, 409613, 197%.

Rouliar, N. H., L. 8. S w l r g , J. Letey, and L. V . Utelu. A p p r o d y t i o n af f i s l d hydraulic conductivity by lat-aratory p m c d u r e a on istlct cores. Soi l S C ~ . Soc. k. Roc.. 36(3), 387-393, 1972.

W i n , Jacob. a d R. V. J pu . Dispersion-affsctd t r u v p o r t of r.lct* w l u t a ia saturated porous dir: M u k i n method applied to . g u i l i b r i m s m ~ o l l e d creb.ng. in unid i rec t ional steady -tar f l w , Water Bssour. ma., 9(5), 133LU56. 1973.

S a f f u n , P. C., .ad C. I. Taylor, a penetration of a f l u i d i n t o a p o m w d i r n or Eels-Shv c e l l contain- a -re .Pi.=- liqtlid, P r a . Royal Soc.. Ssr. A.. 245, 312-331. 1958.

S e l b , X. Sui, a d Don Kirkham, Sctp.9. thrwgh s o i l luddinp o r h i l l a i d e due t o a s t u d y r a i n f a l l ; I. S o i l mrf- of c o a a t m t slap*, S o i l ki. Soc. W. Roc.. 34(3), 402-407, 1972..

Seli.. I. Sami, a d D m Kirkham, Supago cbrowb s o i l b d d w o r a h i l l s i d e due to a s t u d y rainfall: 11. S o i l surface of a r b i t r a r y shape. S o i l Sci. Soe. W . Pmc,. 36(3), 407412, 197%.

Sheinberp, I., I. B r e s l u , and 1. K l ~ u s r a r . S t u d i u on W U m n c m r i l l d l sya-: 1. The swell- pressure, Soi l Sci.. lll. U4-U9, 1971.

Shainberp, I.. a d A. C.i.umaa. S t u d i u o t N.JU m r m i l l o n i t e rY.teUS: 2. The hydraulic c ~ t i v i g , S o i l Sci.. lll. 276-281, 1971.

S i ~ ~ l a i r . L. B., D. W, Fits-, 4 C. L. B l o o 1 . m . P . n u b i l i t y of unurturat.d f i a l d r o i l s u k u l l t e d f m l a b r a t o r y d a u t u r a t i o n data, Trams. k. Soe. Asr. Em., 1 7 0 ) . 399-405, 1974.

may., I. w., E. J. no&, md L. P. R o g g h . Brpcr-ul walusc ion of a uW f o r det- - turaed w r a u l i c w d u e t i v i t y , h a . h r . Soc. Asr. Em.. 16(1), 85-88. 1973.

sliiu, D.. I n f i l t r a t i o n i n t o rterial. ail &i.. UL, 14111.147, 1974.

Mu. D., and A. hmey, liusur-t of m i s t u r a d i t t w i v i t y of vet nrlliPg s y m t u , S o i l Sci.. U6, 391-399, 1973.

wth, w. o., I n f i l t r a t i o n i n cud md its r d a t i o n t o srovod m t e r roeherpe, Water -. Bu.. 3, 539-515, 1967.

Sposito, C.. Volume c h q e s in mulling clays, Soil. 315-320. 1973.

S U r r . J. L., I. E. Broadbent. and D. R. Nialsm. Uitropan t r - f o r u t k

dur* wntinuous luch*. Soi l Sci. Soc. Awr. Proc.. 38(2), 283- 289, 1974.

h m o i t , George R., Effect of a p i c u l m r a l urnagemeat of vat sloping m i l on n i t r a t e and phosphorus i n surface ad sobsurface water, V.tar B ~ M u . . b.. 9(5), 1296-l303. 1973.

St-. Gordon P.. ad R. Allan R a z a . M8theucical simulation of subsurface f l o r contributions t o a ~ l t mnoff. U ~ l d s Creak Uatersbd, Id*, Uatar P.m. Ru. , 10(2), 284-294. 1974.

Berdaniar, C. Uese , Jr.. and U i l l i l n J . Ramm, Obeervatiom of hydraulic conductivity in scae a-Nw Jersey s o i l s , Soi l Sci., 110, 363-364, 1970.

Tabuchi. T.. M i l t r a t i o n and- p a c o l a t i o n i n col- of layered fLus par t ic les packed i n laboratory. ( in Japa-e v i t h E w l i s h -), Trans. kr. Bna. Soc. Jamn. 1, U-19, 1961.

Bematein, L., ad 1. x. Praneois. Ccrpariaom of dr ip , furrow, and sprinkler i r r l8a t ion . Soi l Sci.. 115. 73-86. 1973.

m u r a n L., and G. Comtlntin, Soi l hydraulic conductivity and bulk chrmge. during cycli: c a ~ i u s o d i r r m sxchangs, S* G..

110, 81-85. 1970.

Bhuiyln. S. I.. E. A. W a r , C. H. M. van Bavel, and A. R. Aston, D p a ~ i c a i m l a t i o n of var t ica l M i l t r a t i o n into unsaturated s o i l s , &tar ReMur. Bas., 7(6), 1597-1606. 1971.

I lur ick . A. Wi. A u t h a n t i c a l solution t o a h i l l s i d e seapope p r o b l r . Soi l Sci. Soe. h e r . Proc.. 34(6), 849-853, 1970.

B-, F. T.. S. Davis, and E. W a , Water r&t iom, salt balance .ad n i t r a t e leaching lossas of a 960-acre c i t r u s mtershed, Soi). Sci.. 112, 410-418, 1971.

-k. A. U., Tlm-dependmt l i n u r i z e d i n f i l t m t i o n . I. point sapces , Soi l Sci. Soc. -. PIoc.. 38(3), 383-386. 1974. Bird, N. A., and J . A. McCorquodale, Colputar s b & ~ t i o n of t i l e syst-,

Trans. h r . Soc. Mr. En$.. 1 4 ( U , 175-178, 1971. U l r r t k , A. W., ad D. 0. Lmea. Seepye throuph a h i l l s ide : The s t u d y

water tabla , Water Basour. h.. lO(2). 279-283. 1974. Blake. G.. E. S c h l i e h t i q , and U. Z k r u n n , Water recharge i n a s o i l with shrinluge cracks. Soi l Sci. Soc. her . h e . . 37(5), 669-672, 1973. UoodinO, 8. A.. Cr0undy.t.r p r c b l m of th. int.ractiom of sa l ine .ad

fresh water. S a l L a l t ~ and Water Use, 296 pp.. ed. by T. T.1- and J . R. Philip. W l l a n . Lordon, 1971. Blcvins, 8. L., 8. 8. Bailey, ad G. E. Ballsrd, The effec t of acid mine

water on floodplain s o i l s in the western Kentucky coallfialds, Soil Sci.. UO. 191-196. 1970. Zachmn. David ti., m d M r h W. -. A u t h a v t i c a l i m r u t i c a t i o n

of steady i n f i l t r a t i o n f m 1 h Murces, Soi l Sci. Soc. b a r . Proc.. 37(4). 495-500, 1973. Blight. Geoffrey. E . , Qlw of a i r through sol l s . 1. Soi lneeh. Found.

Div.. Awr. Soc. Civil Enn.. 97(514). 607-624, 1971.

mt. C. W.. Mcdeling the mv.rcnt of c h a i e a l s i n m i l s by vat=. Sci.. 115, 224-230. 1973.

but. C. W.. and Don K i ~ k h n . Auger hole seepage theoq, Soi l Sci. Sac. drr. Proc.. 3Z3) . 365-373, 1971.

Bond, John G., Roy 8 . U i l l h , ad O u r Shadid, Del inut ion of areas for t e r r e s t r i a l dL.ws.l of vasra wrtar. Hater U-. us.. 8(6), 1560-1573, 1972.

EOndarW, A. G.. and V. Kurneuara, Characteristics of the s t ruc ture and l l r a r p of s o h i n the i l r iga ted s o i l q l a r of ths Iran.-Volga region, Sov. Soi l Sci.. 5. 596-603, 1973.

aolldarwa, V. Ya., Experience i n the rue of heavy water (D 0) by Soviet and foreign raseamhers i n the s M y of water i n ph$s, clay minerals and soil*, 242-249. 1971.

BoQdarusv, A. I., Improved m a d l y s h e t u and its loading technique, h. Soi l Sci.. 5, 628-631, 1973.

W. J., J. C. Cowerso. and P. R. -doff, Basing and tas t ing to i q r o v e a o i l adsorption beds. Trams. h r . Soc. &I. b., 17(2), 295-298. 1974.

Eatma, J., U. A. Ziebell, Y. C. Walker, P. C. Olcott. E. McCuy, and F. D. Hole. Soi l absorption of sept ic tank af f lu .n t . 235 pp., I n f o r u t i o n Circular Uo. 20, Wiacomin C.ologica1 aad Natural History Survn/. M i s o n , W i s c o ~ i n , 1972.

--Had,, a., m d 8. 8 . Karbs. m p t h t o groundntar table by r a n e e s.o.int, J. Irri.. Drain. Div.. Amr, Soc. Civi l Bnp.. 97(183), 355-385, 1971.

Abrol. I. P.. d D. R. Mlr. P U studios on ult laaching i n a highly s a l i n e d i c .oil. Soi l Sci.. US. 429-433. 1973.

bhuj.. L. R.. A m r i c a l 4 s i d l a r i t y a d y s i a of i n f i l t r a t i o n in to crusted w i l e , Water U-. b.. 9(4). 987-994. 1973.

Ahujs. L. R.. ad D. Smrtucrdrubar, An Wrond f o m of ro i l -n ts r d i f f w i v i t y fuoction. Soi l Sci. Soc. lur. Roc.. 36(1). 9-14. 1972..

W j a , L. P.. a d D. S v u t r e d n h r , P f f r t of P o r t l a d -t on s o i l ~ y . t i o n a d hydraulic properties. % i l Sci.. 114, 359-366, 1972b.

bhuja, L. P.. acd D. SuPrtsend*, u o r i w n u l s o i l - r t e r i n t a b ' tbrouJh a t h i n wm of reduced p a u b i l i t y , J. Hydml.. 19(1). 71-09, 1973.

Aldabaph. A. 8. Y., .pd h a i g 8. B n r , P b l d m a m r r u a t of hydrwl ic conductivity above a m ta tabla with air--try pa-ta, -. Soc. e. Bna., 14(1), 29-31, 1971.

Al- rn , m. 8.. i n the waUr-phy8ic.l p r o p a t i u of s o i l on -lam l m d used u a p.sarre. h. Soi l Sci.. 4. 707-711. 1972.

Bouyaufos. G.. A new e l e c t r i c a l s o i l ~ ~ i s t u r e mea~ur- d t . Soi l Sfi., G, p. 493, 1972.

Alfam, J. P.. Appl lu t iou of a physical model thenry co predict salt di.plac-t in s o i l s , Soi l Sci.. 112. 364-372. 1971.

B r d t . A., E. Brrsler. I. Diner. I. Ban-Asher, J . k l l r r , and D. Coldbtrg, I n f i l t r a t i o n f r c a a t r i c k l e source: I. P ( l t h u t i c a 1 models, Soil Sci. Soc. drr. Proc.. 35(5). 675-682. 1971.

U i . B. 0 . . and L. C. Bulbart. Rffecm of s o i l c6ture on evaporative l o s s u d a v a i h b l a nta io. s u l - a r i d c l h t u . Soi l Sci.. l l 0 . 328-331. 1970.

Braester. Carol, l4oisture m r l a t i o n a t the s o i l surface ad the advance of the ve t t ing f ront during b f i l t r a t i o n a t contmt flux, Bas-. Us.. 9(3). 687-694. 1973.

Al-Uufaf. 9.. and R. J. thulu. B v r l u t i o n of the f i l t a r - m u mchcd for . s t l u t i n g .oil water ptatl. Soi l Sci.. l l 7 . 194-199. 1974. Breslar, E., J , Heller, N. Diner, I. Ba-Asher. A. Brandt, and D. Coldberg,

I n f i l t r a t i o n f r a P t r i c k l e sourea: 11. Experimmul data d theoretical predictions, Soi l Sci. Soc. h r . Proc.. 35(5), 683- 689, 1971.

&darson, hnupa U., A l h 8. Tice, m d b a s -, The rst-ice p b u e eolposition of c l a y - ~ ~ t u spM.: I. The k ~ 1 i n i t r v a t . r 'ystm, S o i l Sci. Soe. ha. Roc.. 37(6). 819-822. 1973.

Bresler, E., and U. D. Xamper, Soi l -tar evaporation a. affected by wetting .rthads an4 crus t formation. Soil Sci. Soc. h e r . Proc., U ( l ) , 3-8, 1970. -

lnduson. J. U.. 0. P. BLF1.y. m d 8. E. Dregm, Shor t - tua e f t a c t s of inif.tion with high-sodim waters, Sof l Sci.. 113, 358-362, 1972.

Azbbbhir-, b a t , ad mir Oddin A k 4 . A p p r a r t u t c s o l u t i o ~ for r ~ r u t u d y col- d r h g e , Water Ruour. Bu.. 9(2). 401-m, 1973.

Bresler, E.. and D. Yaron. Soi l water regime in ccooolL evaluation of s a l i n i t y i n i r r iga t ion , Water Pasour. Far.. 8(4). 791-800, 1972.

h m i c i , V. S., Percolation of n t a r throvsh P u l l u o soi l s . T a hi& 8 pp., B-1110, T- din. O n i m ~ s i g , Collapa Station,

Texas, 1971.

Brooks. R. 8.. 8 . Ng, C. L. Corey, ad A. 2. Corey, Draiwga of s o i l profiles. J. I r r ip . Drain. Div.. k r . Soe. Civi l Enn.. 97(1R3). 455-467, 1971.

a r t i n Dlrald u., Ilacure ad extent of m e m p o r u i n forea t s o i l s a d t h e i r im~l-e ou ~ b . u d . e a warm .oy.rcnt. 33 pp.. P w -192. VSDA Porasr Senice. 1971.

Broun, Pay U., HP.surcemt of water potential with themacouple psychr-tersr Construction and applicatiom. 27 pp.. Rasearch Paner INT-80, USDA Porest Service. 1970.

Awam, I. a., and T. 0 ' ~ o m d l . I4aviaa nta u b l u in tilm-drdmd .oils, J. Irris. Drain. niv.. drr . Soe. Civi l Bnn.. 9 8 ( I W . 459- 477. 1972.

Bmch. 3.. Jr., and G. Zyrmloski. Solution of q r u t i o n for v e r t i c a l unsaturated flow Of s o i l water. Soi l Sci.. l l 6 , 417-422. 1973.

Brutsaatr. Y i l l n P.. A functional i t e r a t i o n techniqua f o r solving the Richards q u a t i o n a m l i e d t o t!mdisPruionl i n f i l t r a t i o n p r o b l a s , Water Re-. Pns. 7(6). 1583-1596, 1971.

@lor, -d E., an4 Jun-Yvu P a r 4 . . V e r t U I n f i l t r a t i o n in to s la7sr.d s o i l , Soi l Sci. Soc. -I. Roe.. 37(5). 673-676. 1973.

m b r l o l r O b l u , Inf1-e of "bound" n t a r on the ca l ibra t ion of a ncu;ron m i s t u r e r e a r . Soi l Sci.. 114. 323-324. 1972.

Bmtsaert. W i l l e s , N-ricrl solution of ol1tipha.e well flow. J . Hydnul . Div.. Awr. Soc. Civi l En$.. 99(Wll). 1981-2001. 1973.

m, -d C., Prediction of spr* zunoff. Water Buour. Re... 8(4), 9661972. 1972.

W'botko, The effec t of the physical propertlea of s o i l on the deselo-t of the rwt system of apples. Sov. Soi l Sci. . 5, 219-224. 1973.

C~npbell. C. S., and Walter R. Gardmr. P .ychroat r ic measuremat of s o i l water potential: Temperature and bulk d s m i t y ef fec ts . Sci. Soc. h e r . Proc., 35(1). 8-12. 1971.

8.m. K. K.. U. M. Cazleton. 8. n. Taylor, a. I. T h r o c b r t o n , m d G. H V d a n Berg Sd., t i o n of icul tura l Soi ls , 471 pp. , k r . Soc. &r: Bog. z a p h , St.%saph, a h . . 1971.

P.. Soi l s t ruc ture ad its a f f e c t on hydraulic w a d u ~ t i v i t y . ?& sci.. 417-422. 1972.

C-ell. Glen H., ad C. W. Asbell. Ih. effec ts of m i l - p r o f i l e var la t iom and related fac tors on - t r o d e r a t i o n measur-cs. Soi l Sci., && 124-127. 1974.

grnr L. D., Walter H. Dlrdn.r, a d Wilford R. Wrdlur, Soi l Phvsics. i t h Ed., 498 pp., John Uilsy. York, 1972. Carpenter, C. D.. ~ ~ l l s t i o n of s o i l m i % t u r e access tubes in gravels

and eobblas. Soi l Sei. . 113, 453-455, 1972.

Bazilevich, N. I., ad V. M. Ku~achw, Xw-t of s u b s t a m u w i t h surface ad g r a v i t a t i o u d n e a r t i n m i l a of &wchmlc .Uy conjugated ladrrpu of lkraba, Sov. Soi l Sci.. 4, 652665, 1972.

Carmn, E. W., Ed.. The P h t Bwt d Its BmrFrorunt, 691 pp., Univ. Press of Virginia, Chulot tesvi l le . Va.. 1974.

w, J. U., Xsssurillg u-toratd s o i l moisture € l a vith a matar, Soil Sci. Soc. drr. Proc.. 34U). 24-27. 1970. w, Jacob. ~ m - l i q u i d f l o w in porous di.. Mvan. Wdrosci.. 6,

142-252, 1970.

Clry. J. V., Wllibration of s o i l h u t ud vat- flu* r a t e r s , Soi l Sci.. 111, 399-400. 1971. -

Cua, C. n.. and G. P. Cochr.n, T r ~ ~ . f o n w a t i o n of the tLnrsor i o n of Uarcy's U w in iahmgeuemm aad anis tmpic r o i l s , i k t a Resour. paS..(3), 728-733, 1972.

m e a l , D. K., and D. R. UialSen. A 8- st-tion uni t aad loalstic system f o r monitoring watar concsnt of l s r s e s o i l calm, &uw. W.. 7(3), 731-733, 1971.

Chluonl , S u r j i t S., Ronald L. Cox. Dcn W. Green, aad Bharat Ghuuli. -tal and u t h m a t i c a l Imdeling of liquid-liquld &ibla di.plrc-t in po- media, Water Resour. as., 9(5), 1369-1377, 1973.

Child.. E. C., Drainnga of p r o d w a t e r ras t inp on a sloplag bad. &E5 itasow. SU,. 7(5), 1256-1263, 1971.

child., E. c., Concepta of a o i l Water p h e m m e ~ , Soi l Sci.. U3, 246- 253, 1972.

Chow, Celia mmg, and Adrian E. Scheidegpar. S U b i l i t y wcdi t iona f o r fingerlag proces- i n para medi., J. Hydrol.. I S ( l ) , 1-21, 1972.

cba. T. L.. and J. dm Vriu. Dyn8aic -suremat of soil ud ld water potent ia l v l t h a d w b l r loop P e l t i c r type t b r m c o u p l e p .ychreater , soil hi. see. h r . Proc.. 37(2), 181-188, 1973.

Churayrr, I. I.. and n. I. Doroktav, Inv..tisption of n e a r , c d u e t i v i t y i n unsaturated e r t i f i c i a l .oil .).st-. Sov. Soi l Sci.. 2. 329-334, 1970.

Churayev N. V., and N, Ya. Y u h c b d . U t e of water m p a r a t i o n f r m cap;llarie8 of d i f f a . n t d h c a r a Lato m i s t a i r , Sav. Soi l L, 604411, 1973.

Cls ler J a r o l i r , On the tensor cowept of unaaturaced .eisotropic h;dr*ulic conductivity, Wafer Resour. Ru.. 8(2) , 525-528, 1972.

Cis ler J. Note on th. Parlaage uthd for the m r i c a l so lu t ion of L r t d n t a l i d i l t r a t i e n a t m t e r into soil. SOU sci.. 117. 7 ~ + 73, 1974.

Col l i s4aorgc , 8 . . A W a r a t o r y study of i m f i l t r a t m &men. Sci.. 117, 282-287. 1974.

U n r i t t e e on Us-ch of the Irrip. aad main. Div.. Wer ynrOsrwt through i r r i p a t i o n a d d n l r u p a : Provurs , p m b l m , and opportunities, J. I r r i a . Drain, Div.. Amr. Sot. Civil En.., lW(16U1, 153-177, 1974.

Cooley, Richard I., A f i n i t s dide-a ~aehod for unatardy f l w i n variably maturatad porous &is! b p p l i c a t h t o a s ingle w i n g wall, Water Bum m.. 7(6). 1647-1625, 1971.

Carey, JL3$., S. P eter.on ud I4 A. W&t, I lauurewnt of a t t e m u t b of ca .ad 24f:h g u 3 rays ;or s o i l density water content da te l l ina t ion . Soi l Sci. Soc. her . Proc., 35(2). 2.U-219. 1971.

Carniah P II., K B Lary01, and B. J. Bridge, A nondasmretive method of'~oilwinp'mierur. content t w e r a m r a ch.npaa in s o i l s using t h e d a t o r a . S o i l Sel. . 115, 309-314, 1973.

Cmas, 0. E., and P. 0.. Piaehb.eh. Water intake rat- 013 a s i l t 1- s a i l with various muuse a p p l i c a t i o a , Trans. bar. Sac. kr. Em.. 16(2). 282-284, 1973. -

Uagsr,, Gadeon, Perturbation solutions of the dlapmrsioo sgustioa in porous dl-, watsr Pasaur. h a . . 7(1), 135-142, 1971.

D'ae. P., a d I. J. tbrel-seyunu. Substlrfac. dr l f rugc solu t iom by Galerkin's lethad. J. Irrl~. Drain Div.. drr . Sac. Civi l Ens., lW(IB1). 1-15. 1974. -

Wkle, R. J., and C. R. u i l ley . Capillary f r inge datamined LT p a f l o v i n draining sand c o l t m ~ . Trans. Amec Soc. &I. !LUX.. 16(3), 596- 597, 1973.

m-, w i t h e.. ud P* K. nu, ~ i g h herd p - r ~ u r b i l i t y of *and with diaparsed clay par t ic les . Yater beour . itas.. 7(6), 1661-1662, 1971.

Desal, Chandrakant S., %page analysis of sar th banks under d d - , J. Soi l LUch. P o d . Div.. *ur. Soc. Civi l k.. 98(SIal), l l43- 1162, 1972.

EEsri, C. S., A p p r o x h t e so lu t ion f o r w o r d i n s d seepage, J. I r r i a . Drain Div.. h e r . Sac. Civi l b.. 99(IBJ.). 71-87, 1973.

D.8.1, ChandraWnt S., and Walter C. Sherman. Jr., Unconfined t rans ient seepage i n sloping banks. J. S o i l Mech. P o d . Div.. M r . Soc. Civi l Em.. 97(SU2), 357-373. 1971.

Dicker, D., and D. K. Babu, ' h r o - d h n a i o ~ l seepage i n layered s a i l - daa tabi l i s iag ef fec t8 of €1- r i t h an u n s t d y f ree surfat-, Wpt.r h o u r . Reg.. lO(4). 801-809, 1974.

Dickey, Gylan I.. and V i l l i . . R. Johnston, Devalq-t of an l g r i c a t u r a l drainage guide, Trans. Mr. Soc. A s . a4p.. 16(1), 97-99, 1973.

Dirksen. C., Mueurerze.t af hydraulic c d u c t i v i t y by .opus of steady. spherically n m t r i c f l o w . Soi l Sci. Soc. drr . Proc., 38(1), 3- 8, 1974.

Dodolinn, V. T., Bffsct of i r r i g a t i o n r i t h sea$. on the f e r t i l i t y of Sod-Podrolic s o i l s , Sov. Soi l Sci.. 3, 548-555, 1971.

Dolgw, S. I.. aad G. 8. Vinogradova, Capillary-mpma soi l -ur is rnrs C o a M t : iCs p r a e t i d h p o r t m e a and a anr mthod for d e t e m w it, S w . 504. Sci.. 2. 79-85. 1970.

Dolam, 5. I., d G. B. Vinngadwa, Beflactioa eoeEficiant s o i l s , Sov. S o i l Sci.. 5. 735-737, 1973.

Make, R o d d L., and Cclents P. Peteraos, Application of a local s i n i h r i t y eancept in solving the v v r t i i e l aubaurfacs f l w problm, watsr itasour. Rur.. 7(5). 1241-1255, 1971.

Duke, H. R.. E. G. h e . and 0. L. HutcMmm, An autors t ic vacuwa l y s l r t a r for monitoring percolation rates. 12 pp.. 41-165, USM &ricul tura l Iles.areh Semics, 1970.

Dun-, Th-, aad &ha* D. Black, Runoff procesaas drrriw malarclt, Water Bum. h a . , 7(5), 1160-U72, 1971.

htt, G. B., R. W. T e r m t w b . and R. S. Burschkolb, Prediction of Dwum and leaching raquirsmmta for ~ i w ~ f f e c t e d s o i l s , a Sci., 111, 93-103, 1972.

Dlbbs. A.. .nd 5. Schveitzrr, C o w ~ a t i m equations for ncnisothe-1 f l w i n porous d i n , J. Hvdrol., 20(2), 171-180, 1973.

Wlla , A. S.. aad D. W. Uich-, Auger-hole hydraulic conductivity: Firlrt venue second t e s t , T r W , bmcr. Soe. k. En%.. 14(3), 582- 583. 1971.

Dylla, A. S., aid D. I(. S p u r t , RRpotranspirstion (.Luuz-t by chloride translacation, J. mdrol., lO(2). 185-192, 1970.

gdrarda, D. M., P. B. Pkchbach, and L. L. Inms, Nw-t of n i t r s t e a under i t r i ~ c t e d agriculture, Tram. her. Sw. Am, be . . l5(1). 73-75, 1972.

Ehh.lt . D. 8.. Oa the up* of t c i t h r p Q s o i l water md gramduatar, Water h e . Pas.. 9(4), 1073-1074, 1973.

Klliott . L. P., 2. W. MsCalla, N. P. Samson, L. N. Hiellre, acdT. A. Travis, Soi l water n i t r a t e b a t h a broad-banin macd feedlot, harm. Amr. Soc. bg. h.. 16(2), 285-286, 293, 1973.

Bl'llmai, I4. W., l a a c h i q of ea l iae a o i l s r l t h d i f ferent kind. of dra imge, €57- Soi l Sei.. 5, 196-202, 1973.

Elnaggar, I1..urd. 0abor Karadi, and J . Krizek Effect of mm- Dueian brhwior on the character is t ics M t rans ient elor, J. Hydrol., 13(2), l27-138, 1971.

El lin, A., and R. L. Stmet . Seewse f r a ereaebcs throuph mnhmgaraous d s , 3. I r r i n . Drain Div.. -1. Soc. Civil b., 98(IB1). 13-23, 1972.

=-*ify. S. A., Structural c- La tropical s o i l s due to m n i m i n i r r i ' u t i o n m t e r . Soi l Sci.. US, 64-72. 1973.

a f i e l d , C. G., and J. 3. C. Bsieh, 4 p l i c a t i o n of therrroouple peychr-tera t o s o i l =trr tr.nspost. Water Basau. an,, 7(5), 1349-1353. 1971.

Erh, K. T., Application of sp l ine function to ool l s d m e . Soi l Sci . , 114, 333-338, 1972. -

W, K. T., D. R. Nielsen, and 3. W. B i a a r , TWO d b n s i o n a l heat t r snfer i n porous medla v i t h steady-atate water flow, Soi l Sci. $ t i . her . Pmc., 15(2), 209-214, 1971.

F u r e l l , D. A., aad W. B. Larson. M c a of the soil-uater s y s t m dpling I rainstorn. S O U Sci.. 113, 88-95, 1977.1.

Pamall. D. A * , Pod W. E. Lnrson, Hodel* the pore s t ruc ture of p o w &la. Water hsauc . Bas.. 8(3). 699-706. 197Zb.

Pamel l , D. A., and W. E. Larwn, Effef t of intra-egate diffuaioa on osc i l la tory flow dinparaion i n aggregated d i n . Water Re-. -(I>, 185-193, 1973.

Pin*, D. II., Water r a p l l m c y and i n f i l t r a t i o n ras is tancr of organic- film-ooated s o i l s , Soi l Sei. Soc. h r . Proc.. 34(2), 189-194, 1970.

Pin*. D. 8.. aad I(. D. Jackson, An equation f o r denoribing water vapor adsorption i s a t h e m of s a i l s , S a i l Sci., 116, 256-261, 1973.

Pint, D. 8.. and I. S. Nr*.-, Bqurcion f o r describing the f ree swelling o f m n t m r i l l o d t a in water. Soi l Sci.. 116. 355-358. 1972.

P i t a a h u s , D. W., Unsteady radia l flow in partially saturated s a i l s . Trans. bar. SOC. A s . b., l5(5). 912-918, 1972.

litfslmmnm. D. W.. and N. C. Ilowx. Tonsi-ter-orassure trnnsdueer w a t ~ . f o r a ~ y i a g unsteady f l o v through soils. Tram. w. SW. Agr. W.. 15(2>, 272-275, 1972.

Pok, Y r r S 1 , A study of b lo-dbemional i n f i l t r a t i o n , Trans. h r . Soc. nsr. Enn.. 13(2), 676477. 681. 1970.

POL, Yu-St. A. Alvin Bishop, and Charles C. C. Shih, The effec t of i n t s l e equations on the develop-t of the water advance equations f o r surface i r r iga t ion , Tram. Amer. Soc. Am. Eng., 14(5), 801- 802. 803, U71.

Prance, P. W., C. J. Parakh, J. C. Petera, and C. Taylor, Numerical analysis of f r e e surface seepage p r ~ b l e m . J. I r r i p . Drain. D ~ v . ~ b a r . Soc. c i v i l Em.. 9 7 ( m ) , 165-179, 1971.

Reeae, 8. Mlan, I n f l u e ~ c e of the unsrturated flow d-tn on seepage thEough mrth dams, w a t e ~ m o u r . itas., 7(4), 929-941, 1911.

Freeze, 8. Allan, Role of subsurface £1- i n g a r s t i n g s u r f . ~ e runoff, 1. Basa f l w contributions t o channal flaw, Water Resour. Ras., 5(3) , 609-623, 1972.

Pried. J. J.. and N. A. CoPbarnous, Dispersion i n porous media, Mvsn. Evdrasci., 7, 170-282, 1971.

R i t t o ~ , D. D., Dan K l r b , and R. 8. Sh.v, Soi l va ter evaporation. isorha-1 diffvsion, a d heat and watar transfer. Soi l Sfi. Soc. h e r . Pmc.. 34(2), 183-189, 1970.

Cardnor, 8. R., Prediction of -ration from a g c a - s o i l b a e d on the f l w equation, Soi l Sei. Soc. Amr. Roc.. 37(4), 513-516, 1973.

Gardue?, 8. R.. Prediction of *tar l o a s from a fa l l - f i e l d r o i l b a e d oo m i l va ter flow theory. Soi l Sci. Soc. mar. Proc., 38(3). 379- 382, 1974.

Gardner, W t e r e., Gaylon S. *bell, and C. Calissandorff. Syst-tic d random errors i n dual game energy s o i l bulk density and water c a t a n t maussmt, Soi l Sci. Soc. d r r . Proc.. 3 6 0 ) . 393-398, 1972.

k d n e r , W. R., The impact of L. A. Richards upon the f i e l d of s o i l a t o r physics. Soi l Sci.. 1 U . 232-237. 1972. H i l l e l , Daniel. Soi l and Water Ph s i d Principles d Processes,

288 pp.. Academic Prws. LlarYYork, 1971.

Gardner, W. R., The psrmubi l i ty p m b l a , Soi l Sci., 117, 243-249, 1974. l i l l a l , D., and A. Hadas, L M t h e r u l drying of atruecurally Inyored s o i l col tmu, Soi l Sci.. U3, 30-35, 1972.

Gsrdner, W. R., D. Hi l le l , and Y. kny-ini, Poac-irrigation IDO-nt of s o i l water 2. S i m l u l u a u s redis t r ibut ion and evaporation. Resour, Res., 6(4), 1148-1153, 1970.

Hi l le l , D.. V. D. Krentos. and Y. Stylimnou. Procedure and t e s t of an in ternal drainape method for -ring s o i l hy-dmulic eharac ter is t ios i n a i m . Soi l Sai.. 114, 395-400, 1972.

Gee, C. W . , W. Liu, R. Olvang, and 8. E. Jones. h s u r . r e n t and contro l oi n t a r potent ia l i n a s o i l - p l a t syatam. Soi l Sci.. US. 336342. 1973.

Riaun, W. C., and F. Bisal. Percolation r a t e M affected by the in termt ion of freezing and drying processes of so i l s . Soi l Sci.. 115. 102-106. 1973.

Gsl lshvi l i , P. N., Effect of i r r i g a t i o n v i t h thermal waters en the content of .icroelmenes i n .me s o i l s of Georgia, Sov. Soi l Sci.. i. 212-218, 1973.

Harn, M. E.. K s t l u t i n g s o i l parmeability ra tes , J . Trria. Drain. Div., Amer. Soc. Civi l Enn.. 97CIR2). 263-273. 1971.

Gslhar, L. W.. and M. A. Cul l iw. General analysis of lonpitudinrl dispersion i n noamifom f l a , Water Rssour. R u . . 7(6), 1511-1521. 1971.

Hossner, L. 8. . and D. P. Phillips. E x t n c t i m of s e i l solution f r m flooded s o i l using a porous p las t ic f i l t e r , S o i l Sci.. 115, 87-88, 1972.

hrayz.de. A. P., Relationship betvem the eos i f ic ienta of the-1 d i f fus iv i tg and t h s n u l w i r t u r e conductivity in a o i l s , Sov. Soi l u5. 497-499, 1973.

Uaieh, Jack J. C.. and 8. P. Rung.ta. Temperature c q e n s s t a d Pel t ie r psychraatar f o r w r i n g plent and r o i l water potentials. SQFl sci.. 253-257. 1970.

Chavsi , h s d , Jack Keller, and Irving S. Duon, Predicting s o i l density follouinD i r r ip . t ion . Trans. h r . Soc. Asr. h u . , 17(1), 1M-171. 1974.

m. R. 8.. J. N. Luthin. d C. 5. Taylor, Effect of backf i l l on drain f l w i n layered s o i l s , J. I r r in . Drain. Div.. Amer. Soc. Civi l En*.. 100(IR3). 267-275, 1974.

C i a e l , W., M. R q e r , and 0. Strebel. Numerical treatment of t b unsaturated w a t n f l a , up.ation: Capar ison of experimental and w u t e d resul t s , Water Resour. Rgl.. 9(1), 174-177. 1973.

International Association for Hydraulic Rasearch, Pundmntals of Transcart Phommena i n Porous Mia. 392 pp., Elseveir Publ. Co.. Uew York, 1972.

Cifford, Gerald I.. and Rank E. Busby. Intensive infiltrcmeter s tudies on a ploved big uaabrush s i t e , J . Rnirol.. 21(1). 81-90, 1974.

lwnta, S., Thsradywmks of s o i l water: 1. Iha energy concept of s o i l water. S a i l Sci.. 113, 162-166, 19728.

Clobus, A. M., Deslgn, owret ion , ud temperature s e n s i t i v i t y of a thermccouple psyfhrometric moisture potant imeter based on the P s l t i a r e f fec ts , Sov. Soi l Sei.. 4, 745-752. 1972.

Imta, S., T h e d y n a m i c s of s o i l water: 2. The in ternal encr~y and ancrapy of s o i l water, Soi l Sci.. 113, 313-316. 197%.

Iwata, S., On thc def in i t ion of s o i l water potent ia ls M propo.ed by the I.S.S.S. i n 1963, Soi l Sci.. 114. 88-92. 1972~. Globus, A. M.. S. K. Rorenshtok. V. M. Siroekin. and 0. N. Mchurin,

Mthod of determining the ~ i l m i s t u r e potent ia l v i t h a pressure nabraae apparatus, Sov. Soi l Sei.. 3. 90-98, 1971. X n t a , S., Thedynamics of s o i l water! 111. The d is t r ibut ion of

~ a t i o w in a solution i n contact r i t h a charged surface of clay, Soi l Sci.. 117, 87-93, 1974.. Gordiychuk, A. S.. m i g h t of the capi l la ry r i m of r a t e r i n p u t s o i l s ,

Sav. Soi l Sai.. 3. 700-706, 1971. I t m u , S.. T h e d y n a m i c s of s o i l water: IV. Chemical potent ia l of s o i l

water. Soi l Sci.. 117. 135-139. 1974b. Gonut. B., and D. Goldberg, The re la t ion becweeu m i a t u r e -ur .unu with a nautron pmba and s o i l t .rtur+, Soi l Sci., l U , 254-258, 1972. Jackson, R. D., d F. D. Whisler, Equatioas for a p p r a i u r t i n g ver t ica l

namtudy-s t r te drainage of r o i l eo lmns, Soil Sci. Sae. h r . Roe., 34(5), 715-718. 1970. Crane, J . P.. P. L. t h h e y e r , and W. A. mrray , Delayed yield and

unsaturated f l w above a f a l l i n g water table, 48 pp.. T ~ c h p i u r l E.nort &021-!3D. W a t e B.Murces Center, University of W i ~ a i n , W i w a , W i a . . 1972.

Craaa. 8. E.. d J. C. Corer. Calculation of hvdraulic conduct iv ih : A

J u s . R. V. , and Jacob Rubin. Accounting for appsracua-induced dispersion i n amlysas of miscible d iaplacannt u p e r h t s , Hater Basour. -(3), 717-721, 1972.

Jeppson. Roland W., Tr-imt €1- of water f r a infiltr-tera-for~ularion of mathemat id d a l and p r a l M m r y "-rice1 solutions and analyses of resul t s . 50 pp.. PBUG-59C-2. Uuh U.tsr Research Laboratory. L o w , U t & , 1970..

f u r t h e r ~ a v a h u t i o n of &a predictive mthbds, Soi l Sei. Soe. ' h r . Proe.. 35(1), 3-8, 1971.

Grin, A. M.. Correlations between i n t i l t t a t i o n and soil prop.rtiea. Sov. S a i l Sci.. 3. 715-717, 1971.

Jeppson. Roland W., Formlation and solution of transient f l w of water frna an inf l l t rcmeter using the Kirclrboff t r a w f o r u t i o n , 12 pp., PWi059C-3, Utah Water Rrsurch Laboratory. Logan. Utah, 1970b.

Grin, A. n., I n f i l t r a t i o n c a p r i q u a function of physical and chemical s o i l properties, Sov. Soi l Sci.. 4. 453-460, 1972.

JePpson. Roland W.. Determination of hyraulic conductivity-capillary pressure relationship from utura t ion-capi l la ry pressure data from soi ls . 19 pp.. PRYGSSC-4, Utah Water Research Laboratory. Logan, Utah. 1970~.

Duitjem, J . C.. and J- N. Luthin. Effect of s o i l l o i r r u r e hysteresis on the water table p r o f i l e around a gravity w e l l . Weru Resour. p s S . . ( 2 ) . 334-346. 1971.

Cupta, Surandra P.. and Robart A. GreerrLorn. Dispersion during f l w i n porous d i a v i t h bil- adserption, a t e r Resour. h.. 9(5). 13.57-1368. 1973.

Jeppron, Roland W., Solution t o t r n s i e n t ver t ica l m i s t u r c mv-nt based upon saruratiou-capillary pressure data and a m d i f i e d Burdine theory, 46 pp., PWi059C-5. Utah Water Fasearch Laboratory. loerr, Utah, 197W. Gupta, Surendra P.. and Robcrt A. Cmmnbrn. An exper i l rn ta l study of

i a r t o c i b l e d isplacswnc r i t h an unfawrablm m b i l i t y r a t i o i n porous media. Water Basour. Bas.. M(2). 371-374. 1974.. J.ppson, Roland U., Balarioo.hips of i n f i l t r a t i o n c b r a c t e r i s t i e s t o

parmetere daseribirq tbc h y r u l i c proportias of so i l s . 57 pp.. PWC-SP;-?. Utah W t e r R w r c h Laboratory, Logan, Utah, 1972.. Gupu. Sursndra P.. and Robert A. CreeaLorn, Determination of dispersion

and nordinear adsorption parameters f o r f l w i n porous d i a , Hater Reaour. F a . . 10(4), 839-846, 1974b. Jcppacn. Roland W., LMcat iona of gorp f i n i t e difference methods i n

solving the stronply M n l i ~ ~ e a r equation of unsaturated flow in s o i l s , 90 pp., PRVC59C-8, Utah Water Research Laboratory. Logan, Utah, 197%.

Wuk, Ine. Antonio Sor iaw, and Gabor n. b r e d i . ~ l a r t-rd p r i o d i c t i l e d r a b s . J . Hydml.. 19(2), 113-129. 1973.

Jeppwn, Roland W.. and R. Wil l im Nelson, Inverse formlat ion and f i n i t e difference solution t o par t ia l ly saturated seepage from canals. Soi l Sci. Soc. h e r . Proc.. 34(1), 9-14. 1970.

Hun, C. T.. A u r u r yield d s l for -11 watersheds, Hater Resour. u ( 1 1 , 58-69. 1972.

RCdu. A., and D. Hi l le l , Steady-state evaporation through nou-ho~ogmeous r o i l s f r a a shallow n t e r table. Soi l Sci. . 113. 65-73, 1972. Jeppeon. Roland Y., and David L. Schrribar. Solution of a R m - d h w i o n a l .

s tudy-a ta te -tershed f l w s y s t m . Part I . Description of =-tical model. Trans. Amer. Soc. Agr. Enn.. 15(3), 457-463, 1972. 5 j e l a . B. 8 . . and J . n. B b t r u y r , Application of rhmlogica l measuraants

to dete- l iquid 1Mt of s o i l s , Soi l Sci.. 114, 122-130, 1972. Jobling, C. A., and A. K. Tumar. Ph,sical lode1 study of border-scrip

i r r iga t ion . J . I r r i n . Drain Div.. k. Soc. Civi l at.. 99(IR4), 493-511. 1973.

B.11. W. A.. S y s t s u analysis i n i r r i g a t i o n and drainale, J . Hydraul. Div.. h e r . Soc. Civi l Ens.. 99(tIP4), 567-571, 1973.

Rmsm. D. J.. and D. J . lhber. bte- -tic potent ia l by m u d n g f r a t r i n g points of u l i n e n t e r and s o i l s i n the f ie ld . s o i l Sci.. 117. 191-193. 1974. -

Jones. J- W.. and B r a b P. Veru , A d i g i t a l s i d e t i o n of the d-ic s o i l moisture statue. Tram. her. Sot. Ass. %n.. 14(4), 660-664. 1971.

Karadi. Cabor n.. and Gilbert L. Roderick. -tar and vhrsical m d d a 5rt . William 8 . . Subsurface d is t r ibut ion of muurdforrly applied -face waters. T r u u . h r . Sae. Asr. k.. 15(4). 656-6661. 666, 1972. f o r solving~subaurface p r o b l e n in hydrol&y. 43 p& , . ~ e c h n i u l

Report A-029-HIS, Water h s o u r c n Center, Vniversity of Wisconsin. W i a o n , Wia., 1971. Ltuhmi. Hadi T., and C e d d r M. Sliepcevich. Effect of s u p . g e stream

on a r t i f i c i a l s o i l freezing, J. Soi l k h ~ound. h r . ~ o c . c i v i l B n g . , ( S I 4 3 ) , 267-289, 1973. Keller, Jack. Control of s o i l m i a t u r e during sprinkler i r r iga t ion .

I n n s . h e r . Soc. A s . mg.. 13(6), 885-890. 1970. Enukina. R. H., R. F. Ov-. d J . C. Corey. 208~1 and 2 4 ~ p.u

~ u r c e a f o r identifying s o i l water tamed v i t h Dar ter im, Soi l Sei. Soc. Amor. Roe.. 35(2). 199-201. 1971.

Kennedy. C. F., and J. Lielmzs, B u t and mass t ransfer of freezinp water-soil system. Water Resour. Res.. 9(2). 395-400, 1973.

H c d s t r a , W. E., A. T. Corey. d 8. R. Duke. M e l s for aubaurhce drainage. 56 pp.. B d m l o w Pamr tb. 48. Colorado Sta te University, It. Colliaa, Cc.10.. 1971.

Khan, khmmd Yunus, and Don Kirkhan, Spacing af drainage w l l s i n a l a p r e d aquifer , Water Resour. Res., 7(1), 166183, 1971.

Kimbsll, B. A.. VIter vapor ~mreaont through a l c h e o under f i e l d eonditioru, Soi l Sei. *. Amr, Proe.. 37(6). 813-818, 1973. Ea-ier, L. F., Shallow drain parfo-me i n a heavy s o i l , Tr.n..

h e r . Scc. Anr. he. . 16(1). 92-94, 96. 1973. Kinderis, 2 . 8.. Leaching of nutrients by drainage waters, Sov. Soil u, 99-100, 1970.

Rirda, C., D. R. Niolsen. and J . W. B i w r , Siarltaneous transport of

8.k'mmoi.r. L. P., and M. T. Uddah, Field leaching by sprinkler and surface i r r i 8 a t i o n during a crop spawn. T r u u . h e r . Soc. Agr. u ( 2 ) . 275-279. 1974.

chlorlde and m t e r during inf i l t ra t ion . Soi l Sci. Soc. b r . Pme.. x(3. 339-345. 1973.

K i r d . . C., D. 8. Iiisl.en. and J . W. Biggar. The d i d a f t r t s of i n f i l c r a t i o n and redis t r ibut ion on leaching, Soi l Sci.. 117. 323- 330. 1974.

Kirlrhn, D.. Problma .ad t rend. in drainage research. mixed boundary conditiosu, Soi l Sci.. 113. 285-293, 1972.

Kirkham. Don, and W. L. Povers. Mvenced Soi l Phveies, 534 pp.. Wilay- Intsrscienee, N w York, 1972. '

Kissel. D. B.. md J . T. Ritchie, The ef fec t of overburden pressure on c h l o r i d e k water urr.nant-in s rn l l ing clay s o i l . s o i i ~ c i . SOC. h r . P ~ r o . . 3 8 0 ) . 391-394, 1974.

Klute, A. , The detemirut ion of the hydraulic conductivity end dif fus iv i ty of u t u r a t e d s o i l s , Soi l Sei.. 113. 264-276, 1972.

KDvtun, A. P;. bqmved f i e l d methods for d r t d n g the amount of discontinuow capi l la ry moisture, Sov. Soi l Sci., 5, 496-496. 1973.

Kxahn, J.. and D. C. Frdlund; On t o u l , matsic, .ad o s m t i c suction. Soi l Sci.. 114. 339-348. 1972.

Yriseh, 8. J., A. Soriano, and I. Cpk. Unsteady f lov t o bottom drain in bounded aquifer. J . I r r i x . Drain. Div.. &.s. Soc. Civi l Ens., 99(IX2), 169-182, 1973. -

Kuru, V., W. Yutilak. and I. Ylsplr. P.eao~nc~-c.p.citaact s o i l moisture meter. Soi l Sei. . 110. 278-279. 1970.

K w t r , L. T., and S. W. k l s c e d , Uov-nt of chemicals i n s o i l s by water. Soi l Sci.. 115. 231-239, 1973.

h t e p o v , L. Ye., and V. T. Dodolina, Effect on i r r i g a t i o n v i t h ef f luent f r w the Vololp. ch.nicsl cabin . on the agr-liorative charac tar is t ica of l i g h t c h u t n u t clay lo- s o i l s , Sw. Soi l Sci.. 2. 455-465, 1970.

Ui, Suns-ho. and J . J . Jurlnak, Cation adsorption i n o m - d ~ i o n a l f lou rhrowh w i l a : A w r i d solution. Water Re8our. Ras.. 8(1), 99-107, 1972.

Lrl. R., Th. e f f e t of s o i l t a t u r e and density on the neutron and density probe ca l ibra t ton f o r some- t ropica l s o i l s , Soi l Sci.. 117. 183-190, 1974.

LL1. 8 . . and A. C. Pandya. FURW i r r iga t ion v i t h d r r w i n g i n f l w ra te , J. I r r i n . Drain. Div.. h r . Soc. Civi l ha., 96(184). 451- 439. 1970.

Lal. Radhey. and A. C. Padya, V o l m W a c s mthod f o r computing i n f i l t r a t i o n r a t e s i n surface irr*tion, m n a . h e r . Soc. Asr. Enp..(l). 69-72, 1972.

Lmbert, J . L., W. R. Cardner, and J. I. Boyle. Hydrolo& ru-a of a young pine plantation t o weed r u o v a l , Water Resour. Rae.. 7(4). 1013-1019. 1971.

L.-n, D. W. , ~ r o v m a n t r in the f i n i t e difference solution of two- d-iorul dlaprrsion pzoblma. Water W r . Res. . 7(3) . 721-725. 1971.

I..-, C. S.. and L. G. Wilson, Trace element removal f- s-ge ef f luent by s o i l f i l t r a t i o n , Water h o u r . Ras., 7(1), 90-99. 1971.

Laoxnrd, A.. L. Leaf. J. Bergluud, and P. Crml . Annual s o i l moisture- t r p u l t u r e pattarns u influenced by i r r iga t ion , Soi l Sci.. 111, 220-227. 1971.

M. Roland W., md C. Rmphuon, W u u r i u l a d y s i s of elsetro- osmotic flow i n so i la , J . Soll Uuh. Found.. b r . Sac. Civi l h., 99(5118). 603-616, 1973. -

Limn. J-s T.. and T. V. Wilson. DLCD SesDue on P i h n t vatersheds. - 66 pp., Re&rt a. 29. w a t e r ~ R a a o ~ r c u ' ~ s ~ r c h I n s t i t u t e , ~1-. University. Cleuon, S.C.. 1972.

Li-, J. T., and 2. V. Wilson. s o i l p r o f i l e on a P i h n t 16(6), 1100-1103. 1973. -

Distribution of . ~ i s N r . i n the unsaturated mtershed. Tr-. b r . Soc. m. b g _

Lin. Wander, and Don M. Gray, Physical s h l a t i o n of i n f i l t r a t i o n eq+ations. Water Resour. Re'.. 7(5). 1234-1240, 1971.

t i n d e r u n , Charles L.. and Earl C. S t a m , Seasonal variation of hydraulic p a r u e t a r s and the i r influme. upon surface i r r i s a t i o o l p p l l c ~ t i o n *fficiancy. Trans. Awr. Soc. hnr. Ens.. 14(5). 914- 918. 923. 1971.

Liodstrom. P. I.. 4 I. Boersu , Theory of chemical transport with s U u o . o u a wrpt ion in l water saturated porous d i r n , g Sci.. 110. 1-9. 1970.

L i n d s t r a Pb Tr hnd L. Boersn A theory on the mss transport of p r a v b u s l j i i s t r i b u c d c h r i u l s i n a v a t e r - a a t u r a t d sorbing porous mdlm' Soi l Sci.. 111. 192-199, 1971.

~ i n b t m @r T. & L. B M ~ - A c h . ~ r y on the YSS transport of p r e v i o d l y i i s t r i b u t d chemicals L. a weer-saturated sorbing orow medium; 111. Bruct solution f o r first-order k i n e t i c sorption.

% o i l Sci., 115, 5-10, 1973.

Liadstrol. P., L. Soer-, and D. Stockard. A thrary on the u s e transport of previously diaeributed c h d c a l s in a water saturated sorbing p a r w ..dim: I s o t M d u s u , Soi l Sci.. 112, 291-300, 1971.

Laa, D. 0.. .ad A. W. Warrick. Ti r rd .pandent linearized i n f i l t r a t i o n : 11. Line sources. Soi l Sci. Soc. her . Proc.. 38, 568-572, 1974.

Lmb. A. U.. and R. X. Li-ley, Rydrologic CoMequenceS of ra infa l l lugrantation, J. 8vdsaul. Div.. Awr. Soc. Civi l me.. 9 7 W 7 ) . 1065-1080, 1971.

)(.eDonsld. U o l d C., and William P. Waite. Soi l moisture detection v i t h l ug * radars, Water Remur. h.. 7(1), 100-110, 1971.

W c b a n . A., and T. Yagsr. Available water u p a c i t i u of Zambian s o i l s i n ralacion t o p r u s u r e p la te meaaurornts and p a r t i c l e s i r e analysis. Soi l Sci.. 113. 23-29, 1972.

Umaell. R. S., L. C. IL.lond, and R. W. XcCurdy. Coinciience md Interference eorrectioo. f o r dual-margy g- ray .usuremsnts of s o i l d u u i t y a d m t e r content, Soi l Sei. Soc. h e r . Roc.. 37(4). 500-504, 1973.

k r e i , S. M., A b 1 c S h . r 4.1 study of osc i l la t ing w t e r tables i n drained homogenrolu w i l s . Soi l Sei.. U7. 301-305. U74.

Wiw, U. A.. Water-uble fluctuation i n ruponse to recharge. . J . Irrir. h a i n . Div.. Amr. SOC. Civi l Ellg.. 100(=). 31-47. 1975.

K s r i ~ , n. A., Grarth a d d c a y of groundwater m o d s indued Uy p8rcolation. J. Hydrol.. 22014). 295-301, 1974b.

m r t i n . C k l u S., Behviour of porous bed n u r f l w s inpl lar icy , J. Soi l k h . Pound. Div., h r . Soc. Civi l ha.. 97(Sm). 393-415, 1971.

m y b o r a . N. n., The leaching of nut r ients frm grain crops by rain. Sav. Soi l Sci.. 3, 453-458, 1971.

XcCarthy, J. R., Conceptual d y s i . of r a i n f a l l and runoff da ta u i th a hybrid c o q u t e r , Water Resour. Res.. 8(4). 942-955. 1972.

XcHenry. J . Roper, Jer ry C. Ritchie, and h e l a C. Gill . ~ e c d a t i o n of fa l lout ~ u i m 137 i n s o i l s and sediments i n selected watersheds. Water W o u r . W.. 9(3). 676-686, 1973.

Mflntfl., D. S., a d K. J . Iarrw, An inprwed sampling mrhod for -11 undisturbed cores, Sail 239-241, 1972.

&Neal Brian L. J. D. Oster. and J . T. b t c h * r , Calculation of e l e c t r i c s l c&ductivit; f r m sola t ion c-sition d a m u an aid to i n - ~ i t u estimation of .oil s a l i n i t y , Soi l Sci.. 110, 405-414, 1970.

XcQmeen, I. S.. and R. P. Ui l le r . Approximating s o i l &cure c b r a c t e r i s t i c s f m limited d a u : Ellpirie.1 evidence and tantatiWl a d e l , Y.rpr h o u r . h.. 10(3), 521-527, 1974.

LLcYhorter, D. 8.. A. T. Corey, .ad K. n. Me8, The eliminstion of trapped @a f r a porous d i a by diffusion, Soi l Sci.. 116, 18-25. 1973.

b i n . Bursell G., md C w t i s L. Llrson. k d e l l n g the b f i l t r a t i o n -writ of the mintall-runoff p r a e a a , 72 pp., Water Resources Re-rch Centar, University of Mmesota. Kinmapolis. W ~ M . . 1971.

k i n . B u r r d l G.. and Cur t i s L. h r a a o , W a l i n g i n f i l t r a t i o n during a steady ra in , Water Remur. h.. t ( 2 ) . 384-394, 1973.

Uengel. K.. end L. C. Von Braruuuhveig, Tha e f f r t of s o i l moisture ups the a w i l a b i l i t y of potass im ad i t s influence on the growth of young maize plants ( Z u W r s I . ) . Soi l Sci.. l l4 . 142-148. 1972.

tier&, E.. and G. Carlo, The ds taminat ion of s o i l moisture by a t n c t i o n and gea cbromtopraphy. Soi l Sci.. 117. 120-123, 1974.

Uerr i l l , S., and S. Bavliw, Field mea8urement of s o i l water potent is1 u i t h themcouple pyschrouters, Soi l Sci.. 113, 102-109, 1972.

Uichru, I.. and 8. L. Bourcdhs, Seepage f lan-Fie ld da ta mnsurlraunts Ear evaluation of potent ia l contribution of f e r t i l i z e r s t o groundwater pollvtion, Soi l Sci.. 115. 401408. 1973.

Uiller. Raymond J . , Allen R. Overmen, and John W. Klng, k l i n u r vrcer flow through sintared glrss u b r a n e a . Soi l Sci.. 110. 140-165. 1970.

Uillington, L., and R. Shearer, Diffruion i n aggregated porous di., Soil Sci., 111, 372-378, 1971.

w - h a . N. c., c r i t i c a l s a l t wi.e of i r r iga ted s o i l s and sroundvlter drainage in the cotton production zones, Sov. Soi l Sci.. 2, 89- 98, 1970.

mi. H. I.. A. G. Kahykov, md N. I. Bursvcbu*. Study of s o i l piasticity w e r a vide range of s o i l m i r t u r e contmcs, Sov. Soi l u, 600-604, 1972.

Uiy-to, 5 . J . Letey, and J. Oaborn, Water vapor adsorption by water- rcpellekt soil . a t equilibrium, Soi l Sci.. 114, 180-184. 1972.

MY-to. s.. and A. w. warrick. ~ l l t displrfe5ent i n m dra in t i l e s under ponded leaching, Water Bowur. Re.., 10(2), 275-278, 1974.

Uolodt- v. A., and V. V. P a r b v ~ , b s u l t s of l u g e s e a l e lesching of rial; irrig.ted Land in the Golodnsya Stewe. SOP. Soi l Sci.. 2. 479-489. 1970.

&ls, P. J.. Simlacion of port-irrigation m i s m r r m v e a a t . J. I r r i s . Drain. Div.. h r . Soc. Civi l Ens.. 98(IR4), 523-531, 1972.

& l r , P. J . , and I N i n w o n , Extraction term d e l a of s o i l m i s t u s e w e by transpiring plants, Water W o u r . Res.. ((5). 134b-1356. 1970.

morel-sqco~x, H. 1.. A systematic t r w m e n t of &I problM at i n f i l t r a t i o n . 22 pp.. ~ e w r t NO. 23. ~ n v i r o m e n u l ~ e a o u r t h s Center, b l d r e d o S u t e Univksi ty , Pt. Collins, Colo., 1971.

Uorel-Sayt-, 8. J., and J. Khanji, Derivation of an equation of inf i lc ra t ion , Wacer Rasoue. Us . . 10(4), 795-800. 1974.

I I D ~ O M V ~ , N. c.. and v. I. nukhraneli. s o i l emanation a s a function of the m i r t u r e content. Sav. Soi l Sci.. 3. 583-588, 1971.

H ~ ~ P P , Y.ehezlul. Uodified approach t o capi l la ry hys teres is based on a s imi lar i ty hypothesis. Water Resow. Res.. 9(5). 1324-13311 1973.

-1s. Ylch*skel, A conceptual rodel of hysteresis, Water Resour. u ( 3 ) . 514-520. 1974.

Uualck, J . 7.. and D. A. Dusak. A l t e ~ ~ t r f u r r o v i r r i p s t i a n of f ins- t a x t u r d s o i l s , Trans. b r r . Soc. @. Enx.. 17(2), 289-294, 1974.

k s t a f a , n. A. , and J . ~ c t e y , Effect of no -ionic s u r f a c r e n u on penetrability and d i f fus iv i ty of s o i l s , S a i l Sci.. 111, 95-100, 1971.

Uustafa. U. A., J . L e t y . and C. I. Watson. E n h u t i o n of the in t r ins ic- penscrabillty and d i f f u s i v i t y concepts to predict horizontal i n f i l t r a t i o n in porous di., Soil Sci. Soc. Amr. Pme.. 3 4 0 ) . 369-372, 1970.