Reuse Of Drainage Water Research Articles

Assessing drainage water reuse options in Bojili Irrigation District, Shandong

AbstractFor assessing the potential and need to reuse surface drainage and groundwater for sustainable crop production in the Shandong province of the Yellow River basin, inventories were made on the quality of alternative sources of irrigation and on the yields achieved by farmers using those waters for irrigation. Drainage and groundwater quality (EC < 2 dS m−1) in most parts of Huimin and Yangxin counties favors their use for irrigation but there can be some limitations in Wudy as the salinity increases towards the sea. Yield–soil salinity functions were developed for both maize and wheat; for the latter, functions depend upon the number of irrigations applied. Simulations using the SWAP model showed that yields of wheat and maize could be sustained with the reuse of drainage water having a salt content up to 4 mg cm−3. There is a clear benefit from using drainage water for the last two wheat irrigations relative to deficit irrigation despite water salinity. Monsoon rainfall should help to maintain a favorable salt balance, thus to avoid salt build‐up along the soil profile. Results indicate that the reuse of drainage waters offers opportunities for improving irrigation water management in wheat for areas facing water shortage. Copyright © 2006 John Wiley & Sons, Ltd.

Model for the Simulation of Water Flows in Irrigation Districts. II: Application

In a companion paper a model for the simulation of water flows in irrigation districts was formulated. The model combines a series of modules specialized in surface irrigation, open channel distribution networks, crop growth modeling, irrigation decision making, and hydrosaline balance. The objective of this paper is to calibrate, validate, and apply the model, using the Irrigation District Five of Bardenas (Spain) as a study area. Two years of study were used for the analysis, which could be classified as normal (2000) and dry (2001) from the point of view of crop water requirements. Model calibration was performed in one of the 11 hydrological sectors in which the district is divided. The control variable was the monthly water demand, while the calibration variables were related to irrigation operation and scheduling. The seasonal differences in observed and simulated water demand amounted to 0.9 and 1.9% for 2000 and 2001, respectively. Model validation was performed in the rest of the sectors, and the regression line of observed versus simulated monthly water demand could not be distinguished from a 1:1 line in both years. Model application explored scenarios based on management improvement (controlling the irrigation time) and structural improvement (increasing drainage water reuse for irrigation). These scenarios permitted one to sharply reduce water demand, halve the irrigation return flows, and reduce the daily irrigation period from 24 to 16 h.

Reuse of agricultural drainage water in central California: phytosustainability in soil with high levels of salinity and toxic trace elements

Abstract Agricultural drainage waters in the western San Joaquin Valley of Central California contained high levels of salts, boron (B) and selenium (Se). Discharge of the drainage directly into the Kesterson Reservoir was hazardous to plants and wildlife. To investigate the plausibility of using plants as recipients for disposing of poor-quality drainage-waters, multi-year field studies were conducted to reuse drainage water on plants that are salt and B tolerant, and accumulate or stabilize soluble Se from the drainage. Installation of a subsurface tile drainage system in cropping fields allowed drainage waters to be collected and subsequently reused on tolerant plants. The tested plant species included Lactuca sativa, Lycopersicon esculentum, Gossypium hirsutum L., Medicago sativa L., Brassica napus var. Hyola, Helianthus annuus, Distichlis spicata L., and Salicornia bigelovii Torr. The quality of drainage water decreased along the water reuse path, with a sulphate-dominated salinity change from 4.5 to 15.2 dS m -1 ; soluble B from 3.4 to 14.5 mg L -1 ; and soluble Se from 0.08 to 1.18 mg L -1 . Soil salinity and concentrations of B and Se increased with decreasing quality of reused drainage waters. This study demonstrated the importance of monitoring changes in soil quality for sustaining such a plant-based system.

RECIRCULATING NUTRITIVE SOLUTION IN SOILLESS CULTURE OF ROSE USING SALINE ALKALINE WATER

RECIRCULATING NUTRITIVE SOLUTION IN SOILLESS CULTURE OF ROSE USING SALINE ALKALINE WATER

Monitoring management-induced spatio–temporal changes in soil quality through soil sampling directed by apparent electrical conductivity

Characterizing spatial and temporal variability of soil properties at field and landscape scales is tremendously important for a variety of agronomic and environmental concerns including solute transport modeling of non-point source pollutants in the vadose zone, site-specific crop management, and soil quality assessment, to mention a few. Currently, there is a global need to develop tools that evaluate the overall quality of soil to determine the effectiveness and sustainability of farm-management practices. The knowledge now exists for characterizing the spatial variability of soil quality with non-invasive geophysical measurements of apparent soil electrical conductivity (EC a) using mobile GPS-based systems. The objective of this research was to evaluate EC a-directed soil sampling as a means for monitoring management-induced spatio–temporal changes in soil quality. Appraisal was made of a specific management practice, the reuse of irrigation drainage water applied to a saline–sodic soil in central California. A soil quality assessment study was conducted on a 32.4-ha saline–sodic field comprised of 8 rectangular paddocks in California's San Joaquin Valley from August 1999 to April 2002. The study evaluated the spatio–temporal changes that had occurred as a result of irrigation with drainage water over that time period. Using geospatial electromagnetic induction (EMI) measurements of EC a and a spatial response surface sampling design, 40 sites were selected that reflected the spatial variability of the EC a measurements. Duplicate samples were taken at eight selected sites (one randomly selected site from each paddock) to study local-scale variability. At each site soil-core samples were taken at 0.3-m intervals to a depth of 1.2 m and analyzed for 28 physical and chemical properties. Maps created from a geographic information system (GIS) show spatio–temporal changes of four dynamic soil properties (salinity, sodium adsorption ratio, boron, and molybdenum) critical to soil quality, which were strongly and significantly correlated with EC a. Data from 1999 indicate the presence of high salinity, which increased with depth, high sodium adsorption ratio (SAR), which also increased with depth, and moderate to high B and Mo, which showed no specific trends with depth. The application of drainage water for 32 months resulted in leaching of B from the top 0.3 of soil, leaching of salinity from the top 0.6 m of soil, and leaching of Na and Mo from the top 1.2 m of soil. The leaching fraction over the time period from 1999–2002 was estimated to be 0.10. The level of salinity in the reused drainage water (i.e., 3–5 dS m − 1) allowed infiltration and leaching to occur even though high sodium and high expanding-lattice clay levels posed potential water flow problems. Preliminary spatio–temporal analyses from 1999–2002 indicate at least short-term feasibility of drainage water reuse from the perspective of soil quality when the goal is forage production for grazing livestock. The implications of this research extend beyond the provincial applications of assessing drainage water reuse in central California to the global potential of EC a-directed soil sampling for evaluating farm-induced management ramifications on soil quality.

Assessment of irrigation and environmental quality at the hydrological basin levelI. Irrigation quality

Irrigated agriculture notably increases crop productivity, but consumes high volumes of water and may induce off-site pollution of receiving water bodies. The objectives of this paper were to diagnose the quality of irrigation and to prescribe recommendations aimed at improving irrigation management and reducing the off-site pollution from a 15,500 ha irrigation district located in the Ebro River Basin (Spain). Three hydrological basins were selected within the district where the main inputs (irrigation, precipitation, and groundwater inflows) and outputs (actual crop's evapotranspiration , surface drainage outflows, and groundwater outflows) of water were measured or estimated during a hydrological year. The highest volume of water ( I = 1400 mm/year) was applied in the basin with highly permeable, low water retention, flood irrigated soils where 81% of the total surface was planted with alfalfa and corn. This basin had the lowest consumptive water use efficiency (CWUE = 45%), the highest water deficit (WD = 5%) and the highest drainage fraction (DF = 57%). In contrast, the lowest I (950 mm/year), the highest CWUE (62%), and the lowest WD (2%) and DF (37%) were obtained in the basin with 60% of the surface covered with deep, high water retention, alluvial valley soils, where 39% of the cultivated surface is sprinkler irrigated and with only 48% of the surface planted with alfalfa and corn. We concluded that the three most important variables determining the quality of irrigation and the volume of irrigation return flows in the studied basins were (i) soil characteristics, (ii) irrigation management and irrigation system , and (iii) crop water requirements . Therefore, the critical recommendations for improving the quality of irrigation are to (i) increase the efficiency of flood-irrigation, (ii) change to pressurized systems in the shallow and highly permeable soils, and (iii) reuse of drainage water for irrigation within the district. These management strategies will conserve water of high quality in the main reservoir and will decrease the crop water deficits and the volume of irrigation return flows, therefore, minimizing the off-site pollution from this irrigation district.

Issues of scale in water productivity in the Zhanghe irrigation system: implications for irrigation in the basin context

In the context of increased competition for water, growing more rice with less water will be one of the major challenges of the 21st century. This paper examines water savings and issues of scale in water productivity. The main objective is to understand if and how field-scale interventions scale up to subbasin-scale water savings in the Zhanghe Irrigation District (ZID) in Hubei Province, central China. Our results confirmed that on-farm water-saving practices result in higher water productivity per unit of irrigation water at the field scale due to lower irrigation water input. However, the question is, if these field-scale practices have led to “real” water savings; savings which can be transferred to other agricultural and non-agricultural uses without lowering existing production levels. To investigate this question, we examined water use and productivity at four different scales: field scale, meso scale, main canal command scale, and subbasin scale using the water accounting methodology. The study clearly demonstrates the high dependence on the scale of water use and productivity parameters. Depleted fraction and water productivity per unit of gross inflow and irrigation water varied dramatically across scale. Thus, it is not possible to conclude from field-scale observations that basin level water savings will or will not take place. The major reasons for these scale effects are the lateral flow of water across boundaries, differing land use patterns across scales, and changing water management patterns across scales. In the ZID, going from field and meso scale to even larger scales, water productivity per unit of irrigation increases to even higher levels than at the field scale. Here it becomes clear that the ZID, with its possibilities of reuse of drainage return flows and capturing rainfall and runoff in all the reservoirs within the system, is very effective in capturing and using water productively. Factors that influence water productivity and depleted fraction are on-farm water savings as well as the reuse of drainage water, effective capturing and utilization of rain, and canal water management. The scope for additional real water savings in the Zhanghe Irrigation District is limited. Only 13% of the combined rainfall and Zhanghe reservoir irrigation water releases flow out of the basin. A further reduction in drainage surface outflow from the ZID may have negative downstream effects on other water uses, including environmental uses. The main lessons learned are that (1) employing a combination of factors—on-farm practices, reuse, and canal operations—can be an effective means of conserving water resources within irrigation systems, (2) the scope for savings must be considered by an analysis at larger scales (i.e. irrigation system or basin scale), and may be less than thought because of the interactions of these factors. The results clearly indicate that scale effects are important for understanding and planning for water savings and water productivity.

Evaluation of salt-tolerant forages for sequential water reuse systems: III. Potential implications for ruminant mineral nutrition

Reuse of drainage waters is an attractive management option that has been proposed for many irrigated agricultural areas. In California's San Joaquin Valley (SJV), however, drainage effluents are not only saline, but may also contain potentially toxic trace elements such as selenium and molybdenum. Crop suitability for reuse systems depends on the influence the sodium sulfate-dominated waters have on biomass production, plant sustainability, and mineral elements that are critically important for forage quality. Ten promising forage crops were grown in greenhouse sand cultures irrigated with synthetic drainage waters dominated by Na 2SO 4 with an EC of either 15 or 25 dS/m each containing 500 μg/L Se and Mo as SeO 4 2− and MoO 4 2−. Plant material was analyzed three times for mineral content and selected trace elements that may have a profound influence on ruminant health. Trace element concentrations indicate Se toxicity is of little concern, but that high concentrations of both Mo and S in the herbage may lead to Cu deficiency in ruminants. Similarly, high K/Mg and K/(Ca + Mg) ratios in many of the legume and grass forages, respectively, indicate that there may be potential for development of sub-normal Mg levels (hypomagnesaemia) in ruminants. However, each of these disorders can be avoided or corrected with dietary supplements. The most concern regarding ruminant nutrition based on these data is sulfur toxicity. Sodium-sulfate dominated drainage waters will likely elevate forage S concentrations to levels that might cause excessive sulfide concentrations in the rumen and potentially lead to serious neurological disorders affecting animal health.

Evaluation of salt-tolerant forages for sequential water reuse systemsIII. Potential implications for ruminant mineral nutrition

Abstract Reuse of drainage waters is an attractive management option that has been proposed for many irrigated agricultural areas. In California's San Joaquin Valley (SJV), however, drainage effluents are not only saline, but may also contain potentially toxic trace elements such as selenium and molybdenum. Crop suitability for reuse systems depends on the influence the sodium sulfate-dominated waters have on biomass production, plant sustainability, and mineral elements that are critically important for forage quality. Ten promising forage crops were grown in greenhouse sand cultures irrigated with synthetic drainage waters dominated by Na 2 SO 4 with an EC of either 15 or 25 dS/m each containing 500 μg/L Se and Mo as SeO 4 2− and MoO 4 2− . Plant material was analyzed three times for mineral content and selected trace elements that may have a profound influence on ruminant health. Trace element concentrations indicate Se toxicity is of little concern, but that high concentrations of both Mo and S in the herbage may lead to Cu deficiency in ruminants. Similarly, high K/Mg and K/(Ca + Mg) ratios in many of the legume and grass forages, respectively, indicate that there may be potential for development of sub-normal Mg levels (hypomagnesaemia) in ruminants. However, each of these disorders can be avoided or corrected with dietary supplements. The most concern regarding ruminant nutrition based on these data is sulfur toxicity. Sodium-sulfate dominated drainage waters will likely elevate forage S concentrations to levels that might cause excessive sulfide concentrations in the rumen and potentially lead to serious neurological disorders affecting animal health.

Evaluation of salt-tolerant forages for sequential water reuse systemsII. Plant–ion relations

Abstract Implementation of the saline drainage water reuse system proposed for the westside of the San Joaquin Valley (SJV) of California requires development of sustainable cropping systems, which incorporate useful, salt-tolerant agronomic species. Ion composition in the saline drainage effluents present in the SJV is unique, with Na+, SO42−, Cl−, Mg2+ and Ca2+ predominating in that order. To identify potentially suitable crops for reuse systems, 10 forages were tested in greenhouse sand cultures located at USDA-ARS George E. Brown Jr. Salinity Laboratory, Riverside, California. Crops were: alfalfa (Medicago sativa L.) cvs. ‘Salado’ and ‘SW 9720’; narrowleaf trefoil (Lotus glaber Greene) cv. ‘PI 608022’; broadleaf trefoil (L. ulginosus Schk.) cv. ‘Big’; tall wheatgrass (Agropyron elongatum (Host) Beauv.) cv. ‘Jose’; alkali sacaton (Sporobolus airoides Torr.); kikuyugrass (Pennisetum clandestinum Hochst. Ex Chiov.) cv. ‘Whittet’; paspalum (Paspalum vaginatum Swartz) cvs. PI ‘299042’ and ‘Polo’; and bermudagrass (Cynodon dactylon L. Pers.) cv. ‘Tifton’. Two saline treatments, 15 and 25 dS m−1, were imposed. Shoots were sub-sampled for mineral ion analysis when the forages were harvested. Patterns of shoot ion concentrations were unique for each species and varied with salinity level, external ion ratios, harvest date and plant age. Plant preference for K+ over Na+ did not appear to be a reliable predictor of salt tolerance. Salt-tolerant crops, such as kikuyugrass and bermudagrass, were highly selective for K+ (SK,Na ∼ 200 to 400), whereas selectivity coefficients for the equally salt-tolerant grasses, alkali sacaton and tall wheatgrass, ranged from 20 to 40. The forages were highly selective for K+ over Mg2+ despite unusually low K+:Mg2+ ratios in the external solutions. Total-S in the herbage was high and generally increased as external SO42− increased. Based on sustained nutritional health and lack of visual signs of toxicity or deficiency symptoms, several of the forages tested show promise as suitable candidates for the saline–sodic water reuse systems.

Evaluation of salt-tolerant forages for sequential water reuse systems: II. Plant–ion relations

Implementation of the saline drainage water reuse system proposed for the westside of the San Joaquin Valley (SJV) of California requires development of sustainable cropping systems, which incorporate useful, salt-tolerant agronomic species. Ion composition in the saline drainage effluents present in the SJV is unique, with Na +, SO 4 2−, Cl −, Mg 2+ and Ca 2+ predominating in that order. To identify potentially suitable crops for reuse systems, 10 forages were tested in greenhouse sand cultures located at USDA-ARS George E. Brown Jr. Salinity Laboratory, Riverside, California. Crops were: alfalfa ( Medicago sativa L.) cvs. ‘Salado’ and ‘SW 9720’; narrowleaf trefoil ( Lotus glaber Greene) cv. ‘PI 608022’; broadleaf trefoil ( L. ulginosus Schk.) cv. ‘Big’; tall wheatgrass ( Agropyron elongatum (Host) Beauv.) cv. ‘Jose’; alkali sacaton ( Sporobolus airoides Torr.); kikuyugrass ( Pennisetum clandestinum Hochst. Ex Chiov.) cv. ‘Whittet’; paspalum ( Paspalum vaginatum Swartz) cvs. PI ‘299042’ and ‘Polo’; and bermudagrass ( Cynodon dactylon L. Pers.) cv. ‘Tifton’. Two saline treatments, 15 and 25 dS m −1, were imposed. Shoots were sub-sampled for mineral ion analysis when the forages were harvested. Patterns of shoot ion concentrations were unique for each species and varied with salinity level, external ion ratios, harvest date and plant age. Plant preference for K + over Na + did not appear to be a reliable predictor of salt tolerance. Salt-tolerant crops, such as kikuyugrass and bermudagrass, were highly selective for K + ( S K,Na ∼ 200 to 400), whereas selectivity coefficients for the equally salt-tolerant grasses, alkali sacaton and tall wheatgrass, ranged from 20 to 40. The forages were highly selective for K + over Mg 2+ despite unusually low K +:Mg 2+ ratios in the external solutions. Total-S in the herbage was high and generally increased as external SO 4 2− increased. Based on sustained nutritional health and lack of visual signs of toxicity or deficiency symptoms, several of the forages tested show promise as suitable candidates for the saline–sodic water reuse systems.

Assessment of irrigation and environmental quality at the hydrological basin level: I. Irrigation quality

Irrigated agriculture notably increases crop productivity, but consumes high volumes of water and may induce off-site pollution of receiving water bodies. The objectives of this paper were to diagnose the quality of irrigation and to prescribe recommendations aimed at improving irrigation management and reducing the off-site pollution from a 15,500 ha irrigation district located in the Ebro River Basin (Spain). Three hydrological basins were selected within the district where the main inputs (irrigation, precipitation, and groundwater inflows) and outputs (actual crop's evapotranspiration, surface drainage outflows, and groundwater outflows) of water were measured or estimated during a hydrological year. The highest volume of water ( I = 1400 mm/year) was applied in the basin with highly permeable, low water retention, flood irrigated soils where 81% of the total surface was planted with alfalfa and corn. This basin had the lowest consumptive water use efficiency (CWUE = 45%), the highest water deficit (WD = 5%) and the highest drainage fraction (DF = 57%). In contrast, the lowest I (950 mm/year), the highest CWUE (62%), and the lowest WD (2%) and DF (37%) were obtained in the basin with 60% of the surface covered with deep, high water retention, alluvial valley soils, where 39% of the cultivated surface is sprinkler irrigated and with only 48% of the surface planted with alfalfa and corn. We concluded that the three most important variables determining the quality of irrigation and the volume of irrigation return flows in the studied basins were (i) soil characteristics, (ii) irrigation management and irrigation system, and (iii) crop water requirements. Therefore, the critical recommendations for improving the quality of irrigation are to (i) increase the efficiency of flood-irrigation, (ii) change to pressurized systems in the shallow and highly permeable soils, and (iii) reuse of drainage water for irrigation within the district. These management strategies will conserve water of high quality in the main reservoir and will decrease the crop water deficits and the volume of irrigation return flows, therefore, minimizing the off-site pollution from this irrigation district.

Evaluation of salt-tolerant forages for sequential water reuse systems: I. Biomass production

Reuse of saline drainage waters is a management option that has been suggested for the San Joaquin Valley (SJV) of California in order to reduce both the area affected by shallow water tables and the volume of drainage effluent requiring disposal. Salt-tolerant forages may play an important role in this strategy, while at the same time producing a food source for sheep and cattle. Crop selection for reuse systems, however, will depend upon production potential under saline-sodic conditions. To identify potentially suitable crops, a controlled study using an elaborate sand-tank system was conducted at the US Salinity Laboratory to evaluate ten promising forage crops irrigated with synthetic drainage waters dominated by Na 2SO 4 with an EC of either 15 or 25 dS/m each containing 500 μg/L Se and Mo as SeO 4 2− and MoO 4 2−. Forages were cut several times over the year-long duration of the experiment. The forage species tested performed differently in terms of absolute biomass accumulation and biomass production relative to salinity level. Cumulative biomass production of alfalfa ( Medicago sativa L.), a relatively salt sensitive crop, was higher than most other forages at moderate salinity. As salinity increased to 25 dS/m, however, cumulative biomass of the alfalfa cultivars were reduced by nearly half whereas biomass of the most salt tolerant grasses was reduced between 0 and 20%. Although most forage species tested showed promise, those that performed particularly well based on biomass accumulation, overall salt-tolerance, and forage quality were ‘Jose’ tall wheatgrass, bermudagrass and ‘PI 299042’ paspalum.

On‐farm management of saline drainage water in arid and semi‐arid regions

AbstractThe irrigated arid and semi‐arid zones in India face twin problems of overall water scarcity and waterlogging accompanied by salinity. Subsurface drainage has proved successful in the rehabilitation and conservation of waterlogged saline soils. Drainage water from subsurface drainage systems seems to be an important source of water in the next millennium to tide us over the anticipated water scarcity problem in agriculture. However, the drainage waters from subsurface drainage systems are often saline and in the absence of a natural outlet, their disposal creates a problem. Various possible options have been discussed to mitigate the environmental threat posed by low quality drainage waters. Issues relating to potential reuse of low quality drainage waters along with management practices are addressed. Effects of factors influencing the long‐term sustainable use of saline drainage waters are presented and it is emphasized that special management practices have to be followed/evolved for site‐specific water quality, soil, crop and climatic conditions. However, the extent of salt leaching and crop establishment will depend on the total amount of monsoon rains and adequate subsurface drainage. It has been concluded that the use of a part of the saline drainage water in the post‐reclamation phase will not only augment the water supply but also minimize effluent disposal requirements. Copyright © 2004 John Wiley & Sons, Ltd.

Crop and irrigation management strategies for saline-sodic soils and waters aimed at environmentally sustainable agriculture

Irrigation has long played a key role in feeding the expanding world population and is expected to play a still greater role in the future. As supplies of good-quality irrigation water are expected to decrease in several regions due to increased municipal–industrial–agricultural competition, available freshwater supplies need to be used more efficiently. In addition, reliance on the use and reuse of saline and/or sodic drainage waters, generated by irrigated agriculture, seems inevitable for irrigation. The same applies to salt-affected soils, which occupy more than 20% of the irrigated lands, and warrant attention for efficient, inexpensive and environmentally acceptable management. Technologically and from a management perspective, a couple of strategies have shown the potential to improve crop production under irrigated agriculture while minimizing the adverse environmental impacts. The first strategy, vegetative bioremediation—a plant-assisted reclamation approach—relies on growing appropriate plant species that can tolerate ambient soil salinity and sodicity levels during reclamation of salt-affected soils. A variety of plant species of agricultural significance have been found to be effective in sustainable reclamation of calcareous and moderately sodic and saline-sodic soils. The second strategy fosters dedicating soils to crop production systems where saline and/or sodic waters predominate and their disposal options are limited. Production systems based on salt-tolerant plant species using drainage waters may be sustainable with the potential of transforming such waters from an environmental burden into an economic asset. Such a strategy would encourage the disposal of drainage waters within the irrigated regions where they are generated rather than exporting these waters to other regions via discharge into main irrigation canals, local streams, or rivers. Being economically and environmentally sustainable, these strategies could be the key to future agricultural and economic growth and social wealth in regions where salt-affected soils exist and/or where saline-sodic drainage waters are generated.

Economic and agronomic strategies to achieve sustainable irrigation

The achievement of sustainable irrigation in arid regions requires greater attention to waterlogging, salinization, and degradation of ground and surface waters, which are among the problems that continue to threaten productivity and degrade environmental quality. We consider sustainability to be achieved when irrigation and drainage are conducted on-farm, and within irrigation districts, in a manner that does not degrade the quality of land, water, and other natural resources, either on-farm or throughout an irrigated region. Sustainability may also be described as maintaining the productive resources required for irrigation, so that future generations may have the same opportunity to use those resources as we do. Given the increasing importance of irrigated land for food production, the time has come when it is vital to intercept, reuse, and isolate drainage waters within the regions in which they are generated. Adoption of this strategy can be enhanced by policies that require farmers, and irrigation districts, to consider the off-farm impacts of irrigation and drainage. Such policies include linking water rights with salt rights to require the monitoring and management of both irrigation water and the salt loads in drainage waters. We review the knowledge gained since the early 1970s regarding the economic and agronomic aspects of irrigation and drainage, with a focus on drainage water reduction and sequential reuse of drainage water on salt-tolerant crops. Economic incentives that motivate farm-level and district-level improvements in water management are also reviewed. We conclude that adequate knowledge exists for implementing strategies that focus on water use and salt disposal within irrigated regions, and we recommend policies that will motivate improvements in productivity and enhance the likelihood of achieving sustainability.

Effect of Travel Time on Management of a Sequential Reuse Drainage Operation

Sequential reuse of agricultural drainage water recovered in tile lines has been proposed as a strategy for reducing drainage volume in the western San Joaquin Valley of California. In this system, high-quality water is used to grow a salt-sensitive crop, and the drainage from this operation is collected by tile lines and subsequently used on a more salt-tolerant crop. This process is continued on progressively more salt-tolerant species until the final residual is collected and sent to evaporation ponds. In this paper we develop a transfer function model for simulating the drainage concentrations of each stage of a sequential reuse project. Transient salt concentrations are calculated for typical drain spacings and water management strategies, under the assumption that downward movement of water is eventually restricted by a subsurface barrier. Results of the calculations show that response times of fields managed in this way are extremely long, so that the drain lines primarily capture resident ground water for decades or more after the operation is started, especially if the barrier is assumed to be at a substantial depth below the surface. As a result, the system will never reach steady state in any practical period of time, and system design strategies based on steady state behavior will be flawed.

Treatment of agricultural drainage water via lagoon/reverse osmosis system

Treatment and reuse of agricultural drainage water (ADW) is complicated by the presence of soluble organic and inorganic pollutants in addition to hazardous chemicals. Large-scale desalination systems for agricultural drainage water require the development of affordable pretreatment for removal of soluble organic matters, which include residuals of agrochemicals and industrial pollutants. Current reports pertinent to the assessment of the typical characteristics of agricultural drainage water indicate that chemical oxygen demand (COD) concentration ranges from 50–250 mg/l. This paper presents process design features of an integrated scheme for the treatment of agricultural drainage water for reuse in non-agricultural purposes. The system essentially comprises aerated lagoon and two-stage reverse osmosis (RO) or electrodialysis for a plant capacity of 30,000 m 3/d. Results reveal the preliminary technical and economic feasibility of the proposed treatment/desalination system. The capital, operating and unit costs have been estimated. Recommendations for management of brine have been developed.

Effect of high boron application on boron content and growth of melons

Management options for reducing drainage water volumes on the west side of the San Joaquin Valley of California, such as reuse of saline drainage water and water table control, have the potential to adversely impact crop yields due to a build up in soil solution boron concentration. An earlier experiment had shown that extrapolation of B soil tests to field conditions provided poor predictability of B content of melons despite statistically significant relationships. Consequently, three tests for extractable soil B were evaluated for their ability to predict conditions of potential B toxicity in melons grown under controlled conditions. Melons were grown for 95 days in two consecutive years in containers of Lillis soil (very-fine, smectitic, thermic Halic Haploxerert) that had been pretreated with solutions containing B concentrations as great as 5.3 mmol L −1 . Extractable soil B was determined using ammonium acetate, DTPA-sorbitol, and a 1:1 aqueous soil extract at the beginning and end of the experiment. The B treatments caused various deleterious effects on melon growth and development. Fresh and dry plant matter decreased significantly with increasing B concentrations, while B concentration of plant leaves, stems, and fruits increased significantly with increasing B. The number of days to first flowering was significantly delayed from 35 days at B treatments 3 mmol L −1 . Fruit set was completely inhibited at the highest B treatment of 5.3 mmol L −1 . Plant analysis revealed a highly significant relationship between soil extract B obtained with all three extractants and leaf, stem, and fruit B content. Correlation coefficients for plant stems and fruits were much higher than for plant leaves. Correlation coefficients for all soil tests were almost equivalent, although the highest values were obtained for the DTPA-sorbitol extract indicating the greatest predictive capability. The soil tests were well able to predict B damage to melons in a container experiment.

WATER TABLE MANAGEMENT TO ENHANCE CROP YIELDS IN A WETLAND RESERVOIR SUBIRRIGATION SYSTEM

A Wetland Reservoir Subirrigation System (WRSIS) allows for capture, treatment, storage, and reuse of runoff and subsurface drainage waters from cropland, in turn providing both environmental and agricultural production benefits. The three WRSIS sites presently in operation are all located within the northwest Ohio portion of the Maumee River Basin and have been in use for five to six complete growing seasons. WRSIS components include an underground drainage pipe network tied to both a constructed wetland and a water storage reservoir. With this type of system, the drain pipes can be used at different times to either add water (subirrigation) or remove water (subsurface drainage) from the root zone, thereby enhancing crop yields, especially in dry years. Obtaining these crop yield benefits requires a proper water table management approach that includes practicing suggested operational guidelines and initiating as needed system modification improvements. By incorporating a proper water table management approach, and in comparison to control plots, WRSIS subirrigated field crop yield increases for corn and soybeans, respectively, were 34.5 and 38.1% during drier growing seasons, 14.4 and 9.7% during near average to wetter growing seasons, and 19.6 and 17.4% overall.