Jordan Sedlock3/24/15GEOL 305Lab #7 Tri-county water management exercise

The current permits for river water withdrawal are still adequate and based on past history and future projected growth and estimates, this watershed will be able to support and withstand the population growth that is expected to occur over the next ten years. A ten-year tri-county hydrologic history can be found in Table 1 below.

Table 1. 10 year hydrologic history of tri-county watershed

Year Rn Qi Qo T Qp SΔ SΔ (pump)

From river

2012

6.11E+062.09E+0

42.53E+05

1.50E+05 7377562.5

5.73E+06-1.65E+06 1.65E+06

2011

5.83E+062.19E+0

42.42E+05

1.50E+05

7028098.725

5.46E+06-1.57E+06 1.57E+06

2010

4.72E+062.71E+0

41.96E+05

1.50E+05 6678634.95

4.40E+06-2.28E+06 2.28E+06

2009

5.00E+062.56E+0

42.07E+05

1.50E+05

6329171.175

4.67E+06-1.66E+06 1.66E+06

2008

5.27E+062.42E+0

42.19E+05

1.50E+05 5979707.4

4.93E+06-1.05E+06 1.05E+06

2007

5.83E+062.19E+0

42.42E+05

1.50E+05

5630243.625

5.46E+06-1.70E+05 1.70E+05

2006

5.83E+062.19E+0

42.42E+05

1.50E+05 5280779.85

5.46E+061.79E+05

2005

6.11E+062.09E+0

42.53E+05

1.50E+05

4931316.075

5.73E+067.97E+05

2004

5.72E+062.23E+0

42.37E+05

1.50E+05 4581852.3

5.36E+067.73E+05

2003

5.72E+062.23E+0

42.37E+05

1.50E+05

4232388.525

5.36E+061.12E+06

2002

5.55E+062.30E+0

42.30E+05

1.50E+05 3882924.75

5.19E+061.31E+06

Note all units are in m3 water/year

In Table 1, for the years 2007-2012 the population has expanded past the point of sole dependence on its ground water and in order to balance out the deficit, which you can see by the negative values of change in ground water storage, ΔS, the population must draw on the river water supply. This is perfectly acceptable and does not disrupt the river water supply in any way, as the limit of 5.55 *10 6 m3/year is not exceeded. Explanation of final four columns in table to follow.

Table 2 below, contains population and well data useful for calculations and projections.

Table 2. Data by county in tri-county watershedCounty Population Number of

wellsRiver permit

locationsRiver water

permit (m3/year)East River 110,000 27,500 1 3.15E+05

Jordan Sedlock3/24/15GEOL 305Lab #7 Tri-county water management exerciseUpgradient 185,000 46,250 2,3 5.10E+05Downgradient 244,000 61,000 3,4 6.75E+05

Important to note that this data is current as of 2012

Table 3 contains estimates of approximate population data from 2002-2012 knowing that there was a 90% increase in population as well as estimates of approximate population data for 2013-2022 assuming the population will increase to 599,000 residents and gain 15,000 more wells.

Table 3. Estimates and Approximations

Year Population # WellsQp/year

(m3/year)

2022 599,000 149,750 8198812.5

2021 593,000 148,250 8116687.5

2020 587,000 146,750 8034562.5

2019 581,000 145,250 7952437.5

2018 575,000 143,750 7870312.5

2017 569,000 142,250 7788187.5

2016 563,000 140,750 7706062.5

2015 557,000 139,250 7623937.5

2014 551,000 137,750 7541812.5

2013 545,000 136,250 7459687.5

2012 539,000 134,750 7377562.5

2011 513,468 128,367.1 7028098.725

2010 487,937 121,984.2 6678634.95

2009 462,405 115,601.3 6329171.175

2008 436,874 109,218.4 5979707.4

2007 411,342 102,835.5 5630243.625

2006 385,810 96,452.6 5280779.85

2005 360,279 90,069.7 4931316.075

2004 334,747 83,686.8 4581852.3

2003 309,216 77,303.9 4232388.525

2002 283,684 70,921 3882924.75

From 2002-2012, as the population expanded, so did the number of wells available to be drawn from. Qp (Table 1) was found by multiplying the pump per year of 54.75 m3/year by the number of wells assumed to have existed each year. The number of wells each year was found by dividing the assumed population each year by 4 (Table 2). It was assumed that for every 4 people, one well existed (found by dividing the population by number of wells that existed). Once Qp was calculated, ΔS was found by plugging each variable into the following equation: RN +Qi – Qo – T – Qp = ΔS.

Jordan Sedlock3/24/15GEOL 305Lab #7 Tri-county water management exerciseYou’ll notice two difference ΔS values, one that includes the pump of residents drawing their water supply from wells (ΔS with pump) and one that does not include the pump but represents the natural order of the hydrologic cycle (ΔS). As previously stated, in years with a negative value for ΔS, the water was then drawn from the river water supply.

With anticipated population growth, projected pumping (Qp) and change in ground water storage (ΔS) can be determined in the same manner as previously discussed. Table 3 shows all expected and extrapolated data calculated for population per year, wells per year, and anticipated pump per year based on population per year. Using the range of residents in the total population, estimates of population per year were calculated. The number of wells was calculated in the same way as previously described and projected Qp values were calculated in the same way as previously described. These are all based on the assumption that population will increase as projected, however, this may not necessarily be the case, i.e., population could increase faster, or slower, or there could be more residents or less residents than anticipated.

In order to project a value for change in ground water storage, an average for the following was calculated, RN, Qi, and Qo (Table 4). These values were calculated using the data from Table 1.

Table 4. Calculated values of recharge and discharge

AVG Rn min max

5.61E+06 4.72E+06 6.11E+06

AVG Qi min max

2.29E+04 2.09E+04 2.71E+04

AVG Qo min max

2.33E+05 1.96E+05 2.53E+05Note all units in m3 water/year

Plugging these new values into the formerly mentioned equation, RN +Qi – Qo – T – Qp

= ΔS, two cases of ΔS were calculated, a low recharge (incorporating the minimum values in Table 4) case and a high recharge case (incorporating the maximum values in Table 4) which can be found in Table 5 below.

Table 5. Calculated values of low and high recharge to the

hydrologic cycle

Low recharge High recharge

4.74E+06 6.14E+06Note all units in m3 water/year

Jordan Sedlock3/24/15GEOL 305Lab #7 Tri-county water management exercise

The above values are representative of only the first three variables in the same equation that has been used. Considering each case individually, using the low recharge value in Table 5, the same value of T in Table 1, and the calculated value of Qp for 2022 in Table 3, a lower ΔS was calculated (Table 6). Using the high recharge value in Table 5, the same value of T in Table 1, and the calculated value of Qp for 2022 in Table 3, a higher ΔS was calculated (Table 6).

Table 6. Projected S Δ & river water withdrawals

Wells From River

Low SΔ High SΔ High case Low case

-3.80E+06 -2.24E+06 3.80E+06 2.24E+06Note all units in m3 water/year

Table 6 also contains projected river water withdrawals that will be needed based on the deficit that is seen when the population depends solely on well water. In both cases, drawing on the river water supply will be necessary and in both cases, drawing on the river water supply will be feasible and allowable, as the limit of 5.55*106 m3water/year is not exceeded. Based on all of my calculations and projections, this watershed will be able to support the expected population growth over the next ten years.