Effect of brackish water irrigation and straw mulching on soil salinity and crop yields under monsoonal climatic conditions

Fresh water shortages are severally restricting sustainable agriculture development in the North China Plain. The scarcity of fresh water has forced farmers to use brackish water from shallow underground sources, which helps to overcome drought and increase crop yields but also increases the risk of soil salinization. To identify safe and effective ways of using brackish water in this region, field experiments were conducted to evaluate the effect of brackish water irrigation and straw mulching on soil salinity and crop yield in a winter wheat-summer maize double cropping system. The experiment was in a split-plot design. Six rates of straw mulching (0, 4.5, 6.0, 7.5, 15.0 and 30.0 Mg/ha) were assigned to the main plots and two irrigation water qualities (i.e. brackish water with salt content of 3.0-5.0 g/L and fresh water with only 1.27 g salt/L) were applied to subplots. The brackish water irrigation significantly increased the salt content at different soil depths in the upper 1 m soil layer during the two growing seasons. Straw mulching affected the vertical distribution of salt in the brackish water irrigation plots and the average salt content of straw mulch treatments (4.5, 6.0, 7.5, 15.0 and 30.0 Mg/ha) within the 0-20, 20-40 and 0-100 cm soil depths was 10.2, 14.0 and 1.8% lower than that without straw mulch (A₀). No salt accumulation occurred to a depth of 1 m in the brackish water irrigation plots and there was no correlation between the value of SAS (salt accumulated in 1 m of soil) and straw mulch rate. In 2000 and 2001, the salt content within the 0-40 cm soil layer in brackish water irrigation plots increased due to high evaporation rates during April-June, and then decreased up to September as salts were leached by rain. For the fresh water irrigation plots, the salt content remained relatively stable. Straw mulching affected the salt content in the 0-40 cm soil layer in brackish water irrigation plots in different periods of 2000 and 2001, but no correlation between salt content and straw mulch rates was observed except in September of 2000. Unlike for wheat, the yield of maize increased as the straw mulch rate increased according to the equation, y = 0.1589x + 5.3432 (R² = 0.6506). Our results would be helpful in adopting brackish water irrigation and straw mulching in ways that enhance crop yields and reduce the risk of soil salinization. However, long-term effects of brackish water irrigation and straw mulching on soil salinity and crop yield need to be further evaluated for sustainability of the system.     

Effect of seasonal water stress imposed on drip irrigated second crop watermelon grown in semi-arid climatic conditions

A study was conducted to determine the water stress effect on yield and some physiological parameters including crop water stress index for drip irrigated second crop watermelon. Irrigations were scheduled based on replenishment of 100, 75, 50, 25, and 0% soil water depletion from 90 cm soil depth with 3-day irrigation interval. Seasonal crop evapotranspiration (ET) for I₁₀₀, I₇₅, I₅₀, I₂₅, and I₀ were 660, 525, 396, 210, and 70 mm in 2003 and 677, 529, 405, 221, and 75 mm in 2004. Fruit yield was significantly lowered by irrigation water stress. Average water-yield response factor for both of the years was 1.14. The highest yield was obtained from full irrigated treatment as 34.5 and 38.2 t ha⁻¹ in 2003 and 2004, respectively. Lower ET rates and irrigation amounts in water stress treatments resulted in reductions in all measured parameters, except water-soluble dry matter concentrations (SDM). Canopy dry weights, leaf relative water content, and total leaf chlorophyll content were significantly lowered by water stress. Yield and seasonal ET were linearly correlated with mean CWSI values. An average threshold CWSI value of 0.17 before irrigation produced the maximum yield and it could be used to initiate the irrigation for watermelon.     

Maize yield response to deficit irrigation during low-sensitive growth stages and nitrogen rate under semi-arid climatic conditions

Knowledge of crop production in suboptimal environmental conditions not only helps to sustain crop production but also aids in the design of low-input systems. The objective of this study was to evaluate the effects of water stress imposed at low-sensitive growth stages (vegetative, reproductive, and both vegetative and reproductive) and level of nitrogen (N) supply (100 and 200 kg ha⁻¹) on the physiological and agronomic characteristics of two hybrids of maize (Zea mays L.). A two-site field experiment was carried out using a randomized complete block design with three replications and a split-factorial arrangement. A water deficit (WD) was induced by withholding irrigation at different stages of crop development. The results showed that proline content increased and the relative water content, leaf greenness, 100-kernel weight and grain yield decreased under conditions of WD. The highest IWUE was obtained when maize endured WD at vegetative stage at two sites. The limited irrigation imposed on maize during reproductive stage resulted in more yield reduction than that during vegetative stage, compared with fully irrigated treatment. The 100-kernel weight was the most sensitive yield component to determine the yield variation in maize plant when the WD treatments were imposed in low-sensitive growth stages. The results of the statistical regression analysis showed liner relationships between RGR during a period bracketing the V₈ or R₃ stages and 100-kernel weight in all the WD treatments. The increase of N supply improved yield and IWUE when maize plant endured once irrigation shortage at vegetative stage. But, the performance of high N fertilizer reduced and eliminated when water deficit imposed once at reproductive stage and twice at vegetative and reproductive stages, respectively. Furthermore, the response of T.C647 hybrid to increase of N supply was stronger than S.C647 hybrid.     

Agricultural practices,soil fertility management modes and resultant nitrogen leaching rates under semi-arid conditions

Under semi-arid or arid conditions, growing needs for agricultural commodities dictate the intensification of agricultural activities through the application of irrigation and fertilization practices aimed at increasing crop yields. A certain amount of the added irrigation water is designed to seep below the root zone and leach excessive salts accumulated in the irrigated soil. This entails, in part, recharging the ground water-table aquifers. Hence, intensification of agricultural activities introduces a long-term risk of groundwater pollution by unused fertilizers, e.g., nitrogen, salts and pesticides, herbicides, leached from the irrigated fields. To avert or minimize this risk, the amounts of applied water and fertilizer should be determined and minimized by optimizing them to match crop requirements. The objectives of the present work were to determine the amounts of water and salts leached below several agricultural areas subjected to differing soil fertility practices, and to try to relate them to the yields obtained. Published data and experimental data sets of water, chloride and nitrate concentration – depth distributions were used and analyzed. The results show that intensification of agricultural activities leads to increased hazards to surface and groundwater pollution and this can be diminished provided balanced irrigation – fertilization programs are developed for different crops, by using the results of leachate loads seeping from long-term fertility and irrigation studies (permanent plot experiments).     

Irrigation of Lucerne under semi-arid conditions in Cyprus

Summary Three amounts of water –1.0, 0.8 and 0.6 of the irrigation requirement — were used to irrigate lucerne at two frequencies of application — once or twice during each growth cycle. Screened Class A pan evaporation, adjusted by monthly crop coefficients, proved a dependable guide for irrigation. Irrigating once per growth cycle was sufficient, and the highest yield was obtained when the full irrigation requirement was applied. The average annual dry matter yield for the three amounts of irrigation water — 1390, 1110 and 829 mm per year — was 20 285, 16 353 and 12 952 kg ha^–1 respectively, i. e., yield decreased linearly with decreasing amount of water applied. As the water used was saline — with an electrical conductivity of 3 mmhos/cm^–1 — the main root zone became gradually salinized with the drier treatments, while with the wettest treatment salts accumulated below 80 cm depth. Yields were drastically reduced during the hot summer months, even when adequate water was available in the soil profile. This combined with the high irrigation requirement resulted in very low efficiency of irrigation during summer.     

Quantifying risk for water harvesting under semi-arid conditions: Part I. Rainfall intensity generation

Rainfall intensity is the most important factor for runoff estimations, however rainfall intensity data is often unavailable. Rainfall disaggregation techniques are appropriate for use in problems where design storms are required. Rainfall intensity patterns within storms and then the validity of a stochastic rainfall intensity model were, therefore, studied on the highveld of South Africa. Rainfall intensity data collected for 30 years at two semi-arid sites, Bloemfontein (29°S, 26°E) and Pretoria (26°S, 28°E) were analysed using dimensionless hyetographs. No difference was found in either seasonal or geographic variability for the two sites, indicating that intensity patterns within rainfall events across the highveld was identical. The stochastic rainfall intensity model was shown to produce acceptable results. From these results, it has been concluded that one model can be used to generate rainfall intensities for the highveld.     

Quantifying risk for water harvesting under semi-arid conditions: Part II. Crop yield simulation

Risk assessment of maize yield was carried out using a crop growth model combined with a deterministic runoff model and a stochastic rainfall intensity model. These were compared with empirical models of daily rainfall–runoff processes. The combination of the deterministic runoff model and the stochastic rainfall intensity model gave more flexible performance than the empirical runoff model. Scenarios of crop simulation included production techniques (water harvesting, WH, and conventional total soil tillage, CT) and initial soil water content at planting (empty, half and full). The in-field water harvesting technique used in the simulation was a no-till type of mini-catchment with basin tillage and mulching. The lower the initial soil water content at planting, the greater the yield difference between the WH and CT production techniques. With the low initial soil water content at planting, the WH production technique had up to 50% higher yield compared to the CT production technique, clearly thus demonstrating the superiority of the WH production technique. Under all the variations in agronomic practices (planting date, plant population, cultivar type) tested, the WH had a lower risk than CT under these semi-arid climatic conditions (i.e., WH increased the probability of higher crop yields).     

Performance of sugarcane genotypes grown under sodic soil and water conditions

An experiment was conducted to evaluate the effect of residual sodium carbonates (RSC) of irrigation water on the growth and yield of sugarcane grown on sierozem light textured alkaline soil with sodic ground water and to study the performance of some promising sugarcane genotypes under these conditions. Treatments consisted of five levels of irrigations water viz RSC 2.8, 6.5, 12 me l⁻¹ and RSC 6.5 and 12.0 me l⁻¹ fully amended with gypsum. Plant and ratoon crops of eight genotypes of sugarcane were harvested. Cane yield and yield attributing characters like cane height, number of internodes per cane and number of millable canes were recorded. Juice quality viz percent juice extraction, percent sucrose, and commercial cane sugar (CCS%) in juice were determined at the harvest of crop. For both plant and ratoon crops, the average cane yield of all the genotypes of sugarcane and cane yield attributing characters decreased significantly with the increase in RSC of irrigation water to 6.5 and 12.0 me l⁻¹ (35% and 51% decline in the average cane yield for plant crop). For ratoon crop, the corresponding decrease in the average cane yield was less than the plant crop (only 14% and 21%). Amending RSC with gypsum increased the yield in all genotypes. The cane yield of various genotypes obtained under amended RSC with gypsum treatments were almost equal to the yield obtained under RSC 2.8 me l⁻¹ treatment (89% to 92% average cane yield for plant crop and 93% to 96% for ratoon crop). The effect of RSC of irrigation was variable for different genotypes (for example, for the plant crop of CoH 97, 65% and 76% and for CoH 108, 9% and 20% decline in the cane yield was observed with the application of high RSC irrigation water). As compared to plant crop, the ratoon crop of all genotypes recorded higher average cane yield and lesser decline in the cane yield with the application of high RSC irrigation water. Average juice extraction % decreased from 40.5% to 35.8%, and sugar yield decreased significantly (5.61 to 2.91 t ha⁻¹ for plant crop and 6.18 to 5.38 t ha⁻¹ for ratoon crop) with the increase in RSC of irrigation water, and amending RSC with gypsum increased the juice extraction % and sugar yield per unit area.     

Estimation of dwarf green bean water use under semi-arid climate conditions through ground-based remote sensing techniques

Determination of temporal and spatial distribution of water use (WU) within agricultural land is critical for irrigation management and could be achieved by remotely sensed data. The aim of this study was to estimate WU of dwarf green beans under excessive and limited irrigation water application conditions through indicators based on remotely sensed data. For this purpose, field experiments were conducted comprising of six different irrigation water levels. Soil water content, climatic parameters, canopy temperature and spectral reflectance were all monitored. Reference evapotranspiration (ET₀), crop coefficient K_c and potential crop evapotraspiration (ET_c) were calculated by means of methods described in FAO-56. In addition, WU values were determined by using soil water balance residual and various indexes were calculated. Water use fraction (WUF), which represents both excessive and limited irrigation applications, was defined through WU, ET₀ and K_c. Based on the relationships between WUF and remotely sensed indexes, WU of each irrigation treatments were then estimated. According to comparisons between estimated and measured WU, in general crop water stress index (CWSI) can be offered for monitoring of irrigated land. At the same time, under water stress, correlation between measured WU and estimated WU based on CWSI was the highest too. However, canopy-air temperature difference (T_c − T_a) is more reliable than others for excessive water use conditions. Where there is no data related to canopy temperature, some of spectral vegetation indexes could be preferable in the estimation of WU.     

Water stress imposed on muskmelon (Cucumis Melo L.) with subsurface and surface drip irrigation systems under semi-arid climatic conditions

In 2005 and 2006, a study was conducted to determine the effect of subsurface and surface drip irrigation systems and to determine optimum irrigation water using six different irrigation levels imposed on muskmelon (Cucumis Melo L. cv. Ananas F1) under semi-arid climatic conditions. Irrigation treatments received 0, 25, 50, 75, 100, and 125% of class A pan evaporation rates. In 2005, average yield from subsurface and surface drip irrigation systems ranged from 16.2 (I ₀) to 31.1 (I ₇₅) t ha⁻¹ and from 16.2 (I ₀) to 43.8 (I ₇₅) t ha⁻¹, respectively. While in 2006, fruit yields for the same systems ranged from 8.2 (I ₀) to 40.4 (I ₇₅) t ha⁻¹ and from 8.2 (I ₀) to 38.9 (I ₁₀₀) t ha⁻¹. Regression analysis of the yield data indicated no significant (P > 0.05) difference between years and irrigation systems. The highest muskmelon yields from subsurface and surface drip irrigation systems were obtained at 83 and 92% of class A pan. Bigger fruits were obtained with optimum irrigation amounts for both of the irrigation systems. However, there was no clear indication of irrigation water amounts on total soluble solid and flesh thickness of muskmelon fruits.     

Cover crop evapotranspiration under semi-arid conditions using FAO dual crop coefficient method with water stress compensation

Cover cropping is a common agro-environmental tool for soil and groundwater protection. In water limited environments, knowledge about additional water extraction by cover crop plants compared to a bare soil is required for a sustainable management strategy. Estimates obtained by the FAO dual crop coefficient method, compared to water balance-based data of actual evapotranspiration, were used to assess the risk of soil water depletion by four cover crop species (phacelia, hairy vetch, rye, mustard) compared to a fallow control. A water stress compensation function was developed for this model to account for additional water uptake from deeper soil layers under dry conditions. The average deviation of modelled cumulative evapotranspiration from the measured values was 1.4% under wet conditions in 2004 and 6.7% under dry conditions in 2005. Water stress compensation was suggested for rye and mustard, improving substantially the model estimates. Dry conditions during full cover crop growth resulted in water losses exceeding fallow by a maximum of +15.8% for rye, while no substantially higher water losses to the atmosphere were found in case of evenly distributed rainfall during the plant vegetation period with evaporation and transpiration concentrated in the upper soil layer. Generally the potential of cover crop induced water storage depletion was limited due to the low evaporative demand when plants achieved maximum growth. These results in a transpiration efficiency being highest for phacelia (5.1 g m⁻² mm⁻¹) and vetch (5.4 g m⁻² mm⁻¹) and substantially lower for rye (2.9 g m⁻² mm⁻¹) and mustard (2.8 g m⁻² mm⁻¹). Taking into account total evapotranspiration losses, mustard performed substantially better. The integration of stress compensation into the FAO crop coefficient approach provided reliable estimates of water losses under dry conditions. Cover crop species reducing the high evaporation potential from a bare soil surface in late summer by a fast canopy coverage during early development stages were considered most suitable in a sustainable cover crop management for water limited environments.     

Seasonal water use by winter wheat grown under shallow water table conditions

Techniques for estimating seasonal water use from soil profile water depletion frequently do not account for flux below the root zone. A method using tensiometers for obtaining evapotranspiration losses from the root zone and water movement below it is discussed. Soil water flux below the root zone is approached by a sequence of pseudo steady state solutions of the flow equation. Upward soil water flux contributed 36 to 73% to the total water requirement of winter wheat (Triticum aestivum L.) whereas soil water depletion accounted for 11 to 19% only. Water use efficiency with one irrigation during an early stage of plant development is greater than with no or three irrigations. This is the result of both decrease of resistance due to soil moistening and better root development. Tensiometer readings were also interpreted to estimate root zones, water table depths and soil moisture contents. Methods described in this paper can be used in determining seasonal water use by growing crops, replacing or supplementing lysimeter or meteorology approaches to this problem.     

Effects of different emitter space and water stress on yield and quality of processing tomato under semi-arid climate conditions

The objective of the study was to determine the effects of different emitter spaces and water stress on crop yield, such that the tomatoes would be suitable for processing and paste output (Lycopersicon esculentum Mill cv. Shasta). Such variables were also analyzed with respect to crop quality characteristics (e.g., mean fruit weight - MFW, fruit diameter - FD, penetration value of fruit - PV, pH, total soluble solids - TSS, and ascorbic acid contents - AA). The experiment was conducted under ecological conditions typical of the Konya Plain, a semi-arid climate, in 2004 and 2005. Drip irrigation laterals were arranged in such a way that every row had one lateral. Emitters were spaced at 25, 50, and 75 cm intervals in the main plots, while four levels of water supply, irrigation at 7-day intervals with enough water to fill the soil depth of 0-60 cm until capacity was reached (I₁), and 25, 50, and 75% decreased water supply levels were applied as subplots of the experiment. Results of the field experiments showed that yield suitable for processing (68.7-72.7 t ha⁻¹) and paste output (12.2-12.9 t ha⁻¹) were obtainable under conditions of I₁ application (p < 0.01). MFW, FD, PV, and TSS were significantly affected from treatments (p < 0.05). High stress resulted in the highest soluble solids. The total irrigation water amount and water consumptive use of the mentioned application (I₁) were determined as 426 and 525 mm in 2004. In 2005, the total irrigation water amount and water consumptive use of the same treatment were 587 and 619 mm, respectively.     

Supplemental irrigation effect on canola yield components under semiarid climatic conditions

With the availability of irrigation water, supplemental irrigation in winter-grown crops, such as lentil, wheat, and barley, has been intensely practiced to prevent crop yield losses due to the incidence of intermittent drought stress. In the crop growing seasons of 2006-2007 and 2008-2009, a study was conducted to determine the effect of supplemental irrigations on Canola (Brassica napus L. cv. Elvis F1) under the semiarid climatic conditions of the Harran plain, Sanliurfa, Turkey. A sprinkler irrigation system was used to irrigate the study plots. The irrigation treatments included 0.0, 0.25, 0.50, 0.75, and 1.0 (full irrigation) of Class-A pan evaporation amounts. The full irrigation treatment during both years consisted of 250 and 225 mm, respectively. In turn, crop water use values during the same years and treatments were 462 and 449 mm. In general, plant height and 1000 seed weight ranged from 140 to 165 cm and from 2.5 to 3.3 g, respectively, and these variables significantly differed among irrigation treatments (p < 0.05). Crop yield and above ground biomass measurements were affected by irrigation treatments and varied from 1094 to 3943 kg ha⁻¹ and from 6746 to 18,311 kg ha⁻¹, respectively (p < 0.05). Similarly, harvest index values were affected (p < 0.05) and ranged from 0.16 to 0.23 on average. The water use efficiency obtained in the different treatments indicated a strong positive relationship between crop yield and irrigation. Overall, our results indicate that supplemental irrigation substantially increased canola yield; however, for an optimum yield, full irrigation is suggested.     

Fluoride adsorption by a saline sodic soil irrigated with a high F water

Summary Langmuir isotherm data for F adsorption were obtained from 1:10 soil:water extracts of soil samples from a lysimeter study. A sodic silt loam surface soil with a saline sodic subsoil was irrigated with a high sodium chloride, high fluoride (0.38 mMF) geothermal well water. A previous study showed that fluorite (CaF₂) was precipitated from solution in the upper portion of this profile while another mechanism removed F solution in the lower part of the profile to below 0.02 mMF. The Langmuir isotherm data indi cate that one kind of surfaces or sites remove fluoride from solution over the 0 to 1.1 to 1.2 mMF range. The adsorption capacity for this F removal is about 4.4 to 5.8 mmol F/kg of soil and the equilibrium constant is between 0.54 to 1.001/mmol F. Once these surfaces or sites were saturated, a second kind of sites removed F from solution, and had an adsorption capacity of 9.2 to 11.4 mmol/kg and an equilibrium constant of 0.16 to 0.271/mmol. Both data sets fit the Langmuir equation. At some point before or after this second set of sites or surfaces was saturated, the fluorite ion activity product was exceeded and fluoride was then removed from solution via fluorite precipitation. The two adsorption mechanisms lowered the soil solution F concentration sufficiently to prevent ground water contamination, but once the adsorption sites were saturated, fluorite precipitation does not decrease F concentration sufficiently to meet drinking water standards.Contribution from USDA-ARS, Snake River Conservation Research Center, Kimberly, ID 83341, USA     

Simulation of water flow in the soil under sub-surface trickle irrigation with water uptake by roots

Water uptake by roots is presented as a continuous sink function and introduced into the flow equation in the unsaturated zone. The steady-state non-linear equation is linearized and then solved numerically. The results show the influence of water demand, and of the intensity of the water source, on uptake by roots, on leakage under the root zone, and on the progress of the wetting front. The unique feature of this procedure is that it leads to a relatively simple differential equation which is essentially a corrected form of the solutions that disregard the uptake effect and the pressure head at the outlet of the sub-surface emitter. Although further confirmation is needed before the results can be applied for engineering purposes, the general behaviour and flow characteristics in the soil are satisfactorily simulated, and are also validated by the field experiments.     

Effects of gravel mulch on water vapor transfer above and below the soil surface

Laboratory experiments were conducted to investigate the effects of gravel mulch on evaporation with emphasis on resistance to water vapor transfer in a soil-mulch–atmosphere continuum. Based on measurements of evaporation rate using weighing soil columns with and without the surface mulch, the resistance to vapor flow by each of atmosphere, mulch and soil sections was determined. Comparison of experimental results of bare soil with mulched surface indicated that gravel mulch increases the resistance not only above the soil surface but also below the surface. The resistance of the mulch layer to water vapor flow above the soil surface increased exponentially with the thickness of the mulch layer, although so-called “aerodynamic resistance” (i.e. resistance above the mulch–atmosphere interface) slightly decreased compared to the bare soil because of large roughness of gravel mulch. The increase in the resistance below the soil surface, which is conventionally called “soil surface resistance”, is attributed to the development of a dry surface layer. Partial covering of the soil surface with gravel induced concentrated evaporation flux and increased depth of the drying front, even if the soil is relatively wet on spatial average. The nonhomogeneity in soil moisture movement may be reinforced when gravels are partially embedded into the soil.     

Use of thermal units to estimate corn crop coefficients under semiarid climatic conditions

Two crop coefficient equations were derived as a function of fraction of thermal units from lysimeter measured corn evapotranspiration (ET_c-lys) during 1997 and 1998, and reference evapotranspiration obtained from: (a) lysimeter measurements (Kc_mes) or FAO Penman-Monteith (ET_o-PM) estimates (Kc_est-PM). For validation, corn evapotranspiration (ET_c-est) was estimated in 2005 and 2006 from ET_o-PM and: (a) the equation for Kc_mes with (ET_c-est-lyslc) or without (ET_c-est-lys) locally calibrated ET_o-PM; (b) the equation for Kc_est-PM; and (c) the FAO approach (ET_c-est-FAO). The ET_{c-est_lys} estimates showed the lowest bias (0.09 mm day⁻¹); the ET_c-est-PM and ET_c-est-FAO, the highest (0.50-0.51 mm day⁻¹). However, the root mean square error (RMSE, 1.23–1.27 mm day⁻¹) and the index of agreement (IA, around 0.94) of the ET_c-est-lys, ET_c-est-lyslc and ET_c-est-PM were similar. Therefore, ET_c-est-lys is recommended although the ET_c-est-lyslc was similarly accurate. The ET_c-est-PM is less recommended due to poorer bias and systematic mean square error, and a general underestimation except for low corn ET values. For real time irrigation scheduling, the ET_c-est-FAO should be avoided as RMSE (1.35 mm day⁻¹), IA (0.93) and bias were slightly worse, corn ET was overestimated but for high values, and the length of the four phenological stages must be known in advance.     

Simulations of multipurpose water availability in a semi-arid catchment under different management strategies

In the semi-arid Brazilian Northeast, the exploitation of alluvial aquifers for irrigation and domestic supply to rural communities over the last 10 years has upset the traditional mechanisms of water resources management. In the Forquilha watershed (221 km²; 5°17″S, 39°30″W), the two main water resources are reservoirs (with a capacity exceeding 0.9-6.7 × 10⁶ m³), used for domestic water supply only, and an alluvial aquifer (2.3 × 10⁶ m³), used for irrigation and domestic water supply. From 1998 to 2006, the irrigated area with alluvial groundwater increased from 0 to 75 ha, and the fraction of population supplied through domestic water networks, using reservoirs and the aquifer, increased from 1% to 70%. Based on physical and socioeconomic issues, three main water territories have been defined (“Aquifer”, “Reservoirs”, and “Disperse Habitat”). Considering the next 30 years with a realistic population growth, three hypotheses regarding irrigated area (i.e., 0, 75, or 150 ha), and several possible water-management scenarios, hydrological balance models were built and used to simulate the different impacts on water resource availability and salinity. Simulation results showed that, in all cases, releases from the upstream main reservoir are necessary to keep reservoir salinity below 0.7 g L⁻¹ and for guaranteeing domestic needs in the whole watershed. As a consequence, a management approach that takes into account the interrelations among the three territories is necessary. Moreover, the simulations showed that the area of irrigated fields cannot exceed the current extent (75 ha), or serious restrictions on water availability and salinity will take place. Moreover, important socioeconomic problems are expected, including a high cost of palliative water supply with tank trucks from external sources.