APPLICATION OF A GEOGRAPHICAL INFORMATION SYSTEM TO THE STUDY AND ANALYSIS OF THE PROBLEMS DERIVATED FROM THE

SALINITIY OF THE IRRIGATION OF SEGURA RIVER

Guillermo Parra Galant y José Cordero Gracia.

Departamento de Economía Agroambiental, Ingeniería Cartográfica y Expresión Gráfica en la Ingeniería, Escuela Politécnica Superior de Orihuela, Universidad Miguel Hernández de Elche, Ctra. de Beniel, km 3,200 � 03312 Orihuela

(Alicante). gparra@umh.es ABSTRACT Based on outer space information a wide range of relevant technical and economical facts can be incorporated by a Geographical Information System into the data base to complete the analysis and administration of agricultural land. This use has been taken from information obtained from tests made on the soil and irrigation water in the areas of irrigated land on the low plains of the Segura River. Here the level of salinity in the water is a growing problem of great importance. The main effect of salinity is the drop in production and quality of crops, leading to great economic loss, unproductive, barren and abandoned fields. Henceforth, the object of this project is to make a first approach to the outer- space studies of the effects of salinity on crop production on Segura low plains and, therefore, be able to estimate the economic losses brought as a result of it. INTRODUCTION The salinity of water and land in the irrigation areas of the (low plains) �Vega of the Segura River� is a big growing problem. The main effect of the salinity on the crops is the descent of its yields and quality, which are translated into important economic losses. This produces the abandonment of the unproductive lands with its later desertification. To minimize the effect of the salinity several strategies can be followed. The recovery of lands through the depth wash of its salts is the most recommended alternative, but not always the viable one from the technical and/or economical point of view. The correct agronomic handling can solve partially the problem of the salinity, but normally the use of tolerant crops is the only possible or forced option if the salinity is presented in the irrigation water. The tolerance to salinity is a term that is not clearly defined due to the different conceptual focuses that can be carried out. Bernstein (1963) defines it, as the rate which a plant adjusts its osmotic potential with, within a minimum sacrifice of its growth. Shannon (1979): it is the measure of the capacity of a plant to resist the effects of a saline solution concentrated on the root area. Whereas Levitt (1980), associates the tolerance with the absence of negative effects on the growth of the plants and that accumulate the salt in their tissues. Maas (1986) considers that the tolerance can be analysed from three different points of view:

From the aptitude to survive in saline lands. The growth or absolute production in saline lands. The growth or production in a saline land in relation to a non-saline land.

The aptitude to survive can be outstanding from an ecological point of view, but it is a limited approach as agronomic value, since the survival goes often accompanied commercially with production reductions to unacceptable limits. The criterion of the absolute production allows to consider economical valuations under conditions of salinity, but it restricts the comparisons between crops, since the productions are not expressed in comparable terms. Lastly, the third approach allows to compare different crops whose productions are expressed in different units, allowing to analyze the relative levels of salinity that can tolerate not only the crops but also their crops. (Nieman and Shannon, 1977).

Generally, the yield of the crops only diminishes in a significant way if the salinity of the solution of the land overcomes a certain threshold level that is specific for each crop. Above this level, the descent can follow different points. For many crops a falling lineal relationship is continued, as it happens in the majority of the crops intended to the feeding or the production of textile fibre. There are others which approach themselves to null yields and lastly, in some cases, if we start from a certain level, the descent is very abrupt, although before they follow a gradual yield decrease. On the other hand, the apparent symptoms of the salinity damage in plants do not occur until the damage has already taken place (descent in the yields) and then, very little can be made to improve the situation. The measure of the CE (Electric Conductivity) of the saturated extract, considered as reference, supposes an early warning of the possible damages, without waiting the appearance of external signs of affection from salinity. METHODOLOGY AND INSTRUMENTATION From the point of view of the quality of the waters used for the irrigation, the hydrological panorama of the basin of the Segura river, represents the biggest interest, since it is being classified in its biggest part as an arid and semi-arid area. Because of the lack of irrigation, it is not possible an agriculture economically profitable. The continuous use of some high saline concentration irrigation waters could end in the abandonment of highly productive lands. In consequence, the study of the quality of the irrigation water has a great importance, because in spite of being an area with excellent climatic conditions, except from its high imbalance hydric, it presents lands with a very good aptitude for the kind of crops with a great profitability. At the moment, the Segura River is the only course of superficial water able to give water of enough irrigation, so that its influence area acquires a really importance. On the other hand its accused seasonal character would avoid it. Selection of the study area The studies and analysis of irrigation waters of the Segura River carried out by different institutions coincide in the existence of pollution for salinity, sewage sludge and heavy metals. However, the studies of the lands in the �Vega Baja�, contemplating these pollutants, besides being scarce has not been carried out, at least, in the last five years. According to the characteristics of the lands and of the crops, the contamination of the irrigation waters can affect in different measure. The cycles of drought that periodically suffers the basin, give an increase of the salinity in the irrigation waters, causing important losses in the agricultural production. We also need to mention the study carried out by Nieves (1995), about the salinity of irrigation water on the �Vega Baja� lands of the Segura River, where limit values were obtained to which those this type of contamination can arrive. By the right side of the riverbank goes the canal: �Reguerón� or �Azarbe Mayor de Hurchillo� that receives the drainage waters of the agricultural lands and returns them to the Segura River once beyond Orihuela. These waters have a high salinity, because they contain an excessive amount of fertilizers used by the agricultors, as well as washed salts of the agricultural lands. These salts are, together with waste disposals, the main effects causing the increase of salinity of the water of the river descent.

Figure 1. �Vega Baja� of the Segura River. At the beginnings of the 80´s, in the Region of Murcia took place a decent increment of the industrial and cattleman activity that was not accompanied by the corresponding purification of the used waters. There was also an important delay in the purification of the urban waters. The hydric deficit of the basin of the Segura River, induces wastes poured in the river bed as a use of irrigation water in the �Vega Baja�. There is a rising contribution of mainly mud to the agricultural lands. These materials bring some harmful properties for the fertility of the lands, as their high content in heavy metals. In the �Vega Baja� of the Segura river, exist a net of main canals (�Acequias Madre�) or major (�Acequias Mayores�) that take the waters directly from the river and they distribute them among smaller canals: �Acequias Menores�, Arrobas� and �Brazales� to the crops. So, on the Left side of the riverbank, the intersection river � main canals (�Merancho�) takes water from the drain (�avenamientos�) of Murcia and drives them through the Canal: �Acequia Mayor Puertas de Murcia� to the Segura River. Through the right side of the Riverbank, in the limits of the provinces of Alicante and Murcia, the canals: �Acequias Mayores de Molina� and �Alquibla� are born in the Twin Treadmills of Beniel. A bit further before the town �Orihuela�, the canal: �Acequia Mayor de Los Huertos� of the Segura River is born, too. In the �Azúd� de Orihuela� (dump), four Canals are born �Acequias Mayores de Almoravit�, �Escorratel�, �Callosa� and �Acequia Vieja de Almoradí� that ends next to the �Azúd de Alfeitamí� (dump). The selection of the area was carried out according to the possibility of obtaining recent analysis in both water and soil from a number of parcels that were susceptible of contamination. It was also applied to those that are given, a priori, were given some homogeneity in the origin of the irrigation water and in the type of crop problems.

Figure 2. Study area. Process Propose The study and analysis of the yield of the crops in those parcels of agricultural use, watered with the net of canals of the Segura River in the �Vega Baja� area. This study supposes the realization of the following stages:

- Obtaining the most representative and wide field and of analysis information possible on the parcels that are sought to study.

- Setting the analyses parameters of soil parcels that are considered independent variables. - Purify the information until obtaining a really reliable information. - Application of the SIG, with the incorporation of the obtained field data, and the achievement of new variables

by means of space analysis. - Obtaining a new field data that develop the study along the controlled area. This would be enable to design a

mathematical pattern that being based on statistical techniques, allows to estimate unknown information based on the known and available data.

- Analyze the importance of independent variables being able to eliminate, those that have a scarce influence in the formation of the price.

In short, being able to build an administration and an analysis system of the effects of salinity in the crops based in GIS tools. Obtaining of field data In this work the Segura River water, in its itinerary through the end of the province of Murcia, was analyzed in the following sampling points: �Merancho area� (Murcia). �Norias gemelas, Sifón Trasvase Tajo-Segura y Orihuela� area (Alicante). We take soil samples, from irrigated areas by the canals: �Alquibla�, �Molina�, �Los Huertos�, �Puertas de Murcia�, �Almoravit�, �Escorratel�, �Almoradí�, and �Comuna� (�Alcudia - Los Huertos�). Also from �Merancho�, �Reguerón� and �Trasvase Tajo- Segura� (transfer) on the left side if the riverbank in Elche.

Figure 3. Characteristics of the canals. The obtained results are shown in the Figure 4, where levels of electrical conductivity and the potentially toxic elements (chlorides, sodium and boron) are gathered.

shows Origin of the water Situation EEC Cl - Na+ B

nº (dS/m) (mmol/l) (mmol/l) (mmol/l) 1 Puertas de Murcia Orihuela 3,28 13,80 16,78 1,21 2 Puertas de Murcia Orihuela 2,53 9,60 12,00 1,29 3 Molina Hurchillo 6,00 26,00 25,74 1,10 4 Molina Orihuela 5,72 23,00 24,96 1,45 5 Callosa Orihuela 3,92 14,30 15,91 1,31 6 Almoravit Orihuela 5,45 30,90 27,22 1,22 7 Los Huertos Molins 3,77 17,30 16,52 1,14 8 Callosa Callosa del Segura 4,32 19,20 19,13 1,01 9 Escorratel Orihuela 3,47 16,50 17,57 1,07 10 Los Huertos Rojales 2,70 10,00 10,00 0,99 11 Alcudia Rojales 4,67 13,40 17,74 1,62 12 Merancho El Raal 2,56 7,40 8,26 1,51 13 Río Segura Desamparados 3,41 12,20 12,87 1,39 14 Río Segura Benejúzar 1,21 3,00 4,35 0,68 15 Alquibla Benejúzar 1,60 4,80 6,26 0,54 16 Vieja de Almoravit Benejúzar 1,54 4,80 6,17 0,58 17 Mayayo Benejúzar 1,75 5,60 8,61 0,96 18 Trasvase Tajo-Segura Elche 1,92 5,50 5,74 0,63

Averages 3,32 13,18 14,21 1,09

Figure 4. Results of the total salinity and potentially toxic elements.

Figure 5. Points of analysis of samples along the Segura River

Nº 1 2 3 4 5 6 7 8 9 CE (dS/m)

CROP 3,28 2,53 6,00 5,72 3,92 5,45 3,77 4,32 3,47 Tomato 92,57 92,57 66,67 69,33 86,48 71,90 87,90 82,67 90,76

Cucumber 89,60 89,60 53,33 57,07 81,07 60,67 83,07 75,73 87,07 Spinach 90,15 90,15 69,23 71,38 85,23 73,46 86,38 82,15 88,69 Celery 90,86 90,86 74,07 75,80 86,91 77,47 87,84 84,44 89,69

Cabbage 85,49 85,49 58,82 61,57 79,22 64,22 80,69 75,29 83,63 Potato 80,96 80,96 48,19 51,57 73,25 54,82 75,06 68,43 78,67 Corn 80,96 80,96 48,19 51,57 73,25 54,82 75,06 68,43 78,67

Pepper 74,93 74,93 36,62 40,56 65,92 44,37 68,03 60,28 72,25 Lettuce 74,29 74,29 38,96 42,60 65,97 46,10 67,92 60,78 71,82 Radish 72,99 72,99 37,66 41,30 64,68 44,81 66,62 59,48 70,52 Onion 66,45 66,45 22,58 27,10 56,13 31,45 58,55 49,68 63,39 Carrot 67,89 67,89 29,58 33,52 58,87 37,32 60,99 53,24 65,21 Turnip 78,56 78,56 54,05 56,58 72,79 59,01 74,14 69,19 76,85 Palm 100,00 100,00 92,86 93,86 100,00 94,82 100,00 98,86 100,00

Grapefruit 76,13 76,13 32,26 36,77 65,81 41,13 68,23 59,35 73,06 Orange tree 74,92 74,92 31,75 36,19 64,76 40,48 67,14 58,41 71,90 Almond tree 66,42 66,42 15,09 20,38 54,34 25,47 57,17 46,79 62,83

Lemon tree N.Amargo 81,63 89,46 53,24 56,16 74,95 58,98 76,51 70,77 79,65 Lemon tree M.Cleopatra 83,61 93,85 46,45 50,27 74,86 53,96 76,91 69,40 81,01

Lemon tree C.Macrophylla 70,13 82,31 25,97 30,52 59,74 34,90 62,18 53,25 67,05

Figure 6. Maximum yields of some crops of the Low Vega of the Segura River, (according to the salinity levels analyzed in each sample).

Nº

10 11 12 13 14 15 16 17 18 CE (dS/m)

CROP 2,70 4,67 2,56 3,41 1,21 1,60 1,54 1,75 1,92 Tomato 98,10 79,33 99,43 91,33 100,00 100,00 100,00 100,00 100,00

Cucumber 97,33 71,07 99,20 87,87 100,00 100,00 100,00 100,00 100,00 Spinach 94,62 79,46 95,69 89,15 100,00 100,00 100,00 100,00 100,00 Celery 94,44 82,28 95,31 90,06 100,00 100,00 100,00 100,00 99,26

Cabbage 91,18 71,86 92,55 84,22 100,00 100,00 100,00 100,00 98,82 Potato 87,95 64,22 89,64 79,40 100,00 100,00 100,00 99,40 97,35 Corn 87,95 64,22 89,64 79,40 100,00 100,00 100,00 99,40 97,35

Pepper 83,10 55,35 85,07 73,10 100,00 98,59 99,44 96,48 94,08 Lettuce 81,82 56,23 83,64 72,60 100,00 96,10 96,88 94,16 91,95 Radish 80,52 54,94 82,34 71,30 99,87 94,81 95,58 92,86 90,65 Onion 75,81 44,03 78,06 64,35 99,84 93,55 94,52 91,13 88,39 Carrot 76,06 48,31 78,03 66,06 97,04 91,55 92,39 89,44 87,04

Turnip 83,78 66,04 85,05 77,39 97,21 93,69 94,23 92,34 90,81 Palm 100,00 97,61 100,00 100,00 100,00 100,00 100,00 100,00 100,00

Grapefruit 85,48 53,71 87,74 74,03 100,00 100,00 100,00 100,00 98,06 Orange tree 84,13 52,86 86,35 72,86 100,00 100,00 100,00 99,21 96,51

Almond tree 77,36 40,19 80,00 63,96 100,00 98,11 99,25 95,28 92,08 Lemon tree N.Amargo 87,68 67,12 89,14 80,27 100,00 99,16 99,79 97,60 95,82

Lemon tree M.Cleopatra 91,53 64,62 93,44 81,83 100,00 100,00 100,00 100,00 100,00 Lemon tree C.Macrophylla 79,55 47,56 81,82 68,02 100,00 97,40 98,38 94,97 92,21

Figure 7. Yields of some crops of the Low Vega of the Segura River, (according to the salinity levels analyzed in each

sample).

Figure 8. Thematic map of soil electrical conductivity - CE (dS/m)

Figure 9. Ranges of decrease of the yield in lettuce (according to the soil electrical conductivity).

Figure 10. Ranges of decrease of the yield in lemon tree (according to the soil electrical conductivity).

Figure 11. Ranges of decrease of the yield in citric (according to the soil electrical conductivity).

Figure 12. Decrease of the yield in vegetables (broccoli, spinach, celery, cabbage and lettuce, etc) (according to the soil electrical conductivity).

CONCLUSIONS The use of the GIS has revolutionized the cartography world. The successive applications to other fields have been caused important changes in the way of working with geographical data. The study and administration of yields crops in the analyzed parcels is not an isolated operation. It supposes a process, where, on one hand, they should be located accurately cartographically for their space analysis and, on the other hand, associate it with their agronomical characteristics and results of the carried out analyses. The GIS is a powerful tool for the capture, storage, manipulation and analysis of the information, not only geographical information but also as technical and economic data. Its capacity to manage and integrate information of multiple origins allows us an analysis that would result pragmatically inaccessible for the conventional methods. Under this way it is obtained a better knowledge of the effects of salinity on the crop parcels in the study area that drives us to an easier way for the best management in the same crops. In a concrete area of irrigable (where the soil of crop parcels has been analyzed), has been settled down a series of ranges on the decrease of the yields of different common crops which allow to know the effects that produced by irrigation water salinity. This space analysis allows to establish relationships among a fundamental economic variable - the profitability of a crop - with other variables, with the following ones characteristic:

- Geographical: surface, situation, origin of the irrigation water, etc. - Technical: crop type, irrigation system, plantation frame, fertilization, etc.

This way it is possible to analyze geographically (by means of the relationship among all the variables) the effects caused by salinity, allowing the identification problems as in an extensive irrigation land, as in concrete parcels. By the information collected by the GIS, we reach in a easier way, mainly with a geographical vision and by means of diverse strategies (related to the agronomical handling of the parcels: crop type�) to try to reduce the negative effects of salinity. It is even possible its use as a tool of help in the genetic improvement. The future aims the possibility to maintain and to update the GIS application, developed in the present work, with the obtaining of new data (soil and water analysis, crop types, real productions, etc). It is also possible to prepare the land cartography level of the study area. This will complete a perfect database that would help us to study the evolution of the salinity and like the yields of the crops are affected in the Low Vega of the Segura river.

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