Evaluation of Water and Energy Use in Pressurized Irrigation Networks in Southern Spain

A procedure for evaluating water and energy use in pressurized irrigation networks was developed. Performance indicators were derived from the International Program for Technology and Research in Irrigation and Drainage (IPTRID) and the Institute for Diversification and Energy Savings (IDAE) in Spain and applied to ten representative irrigation districts with on-demand pressurized networks during the 2006–2007 irrigation season. The results confirm the high energy requirements needed for operating these irrigation schemes. To apply an average depth of 2,589??m3/ha, the energy required was estimated to be 1,000??kW???h/ha. Power requirements per unit of irrigated area were 1.56??kW/ha and the pumping energy (PE) efficiency was 58%.     

Performance-Based Optimization of Land and Water Resources within Irrigation Schemes. I: Method

Optimum land and water allocation to different crops grown in different regions of an irrigation scheme is a complex process, especially when these irrigation schemes are characterized by different soils and environment and by a large network of canals. At the same time if the water supply in the irrigation schemes is limited, there is a need to allocate water both efficiently and equitably. This paper describes the approach to include both productivity (efficiency) and equity in the allocation process and to develop the allocation plans for optimum productivity and/or maximum equity for such irrigation schemes. The approach presented in this paper considers the different dimensions of equity such as water distribution over the season, water distribution during each irrigation, and benefits generated. It also includes distribution and conveyance losses while allocating water equitably to different allocation units. This paper explains the approach with the help of the area and water allocation model which uses the simulation–optimization technique for optimum allocation of land and water resources to different crops grown in different allocation units of the irrigation scheme.     

Agroecological Impacts from Salinization and Waterlogging in an Irrigated River Valley

Extensive field data and calibrated flow and salt-transport models characterize the spatial and temporal patterns of salinity and waterlogging in an irrigated western river valley. Over three irrigation seasons, average seasonal aquifer recharge from irrigated fields in a 50,600?ha study area ranges from 0.59?to?0.99?m, including contribution from precipitation. The salinity of irrigation water varies from 618?to?1,090?mg/L. The water table is shallow, with 16 to 33% of irrigated land underlaid by an average water table less than 2?m deep. Average water table salinity ranges from 2,680?to?3,015?mg/L, and average soil salinity from 2,490?to?3,860?mg/L. Crop yield reductions from salinity and waterlogging range from 0 to 89% on fields, with regional averages ranging from 11 to 19%. Annual salt loading to the river from subsurface return flows, generated in large part by dissolution from irrigation recharge, averages about 533?kg/irrigated?ha?per?km. Upflux from shallow water tables under fallow ground contributes to about 65?million?m3 (52,600?acre-ft) per year of nonbeneficial consumption. Beyond problem identification, the developed database and models provide a basis for effectively addressing these problems through a systematic and comparative assessment of alternative solutions.     

Productivity and Equity of Different Irrigation Schedules under Limited Water Supply

Some irrigation schemes with limited water supply in Central and Southern India follow the area proportionate water distribution based on assumed uniform characteristics of the command area (planned schedule). However in most cases, this planned schedule is overridden by the practice in which users at head draw more than their share of water (actual schedule) due to human factors and technical limitations of the planned schedule. This practice is highly inequitable as users at tail end do not get any water. This paper considers alternative schedules based on full irrigation or deficit irrigation within the framework of area proportionate water distribution in such irrigation schemes and presents the simulation–optimization technique to develop the corresponding land area and water allocation plan for different allocation units by considering the heterogeneity of the irrigation scheme. This paper further demonstrates the utility of proposed alternative schedules by comparing the productivity and equity of these schedules with planned and actual schedules for one irrigation scheme in Central India. The results show that the actual schedule reduces both productivity and equity greatly and the productivity and equity with the alternative schedules are higher than with the planned schedule. The results also show that deficit irrigation has great potential to increase both productivity and equity of irrigation schemes.     

Feasibility of Using Natural Zeolites to Remove Sodium from Coal Bed Methane-Produced Water

Coal bed methane (CBM) is naturally occurring methane, contained in coal seams saturated with water. In order to extract the CBM, large quantities of water must be pumped from the coal seams. CBM water, produced in some areas of New Mexico, contains low total dissolved solids, which can potentially be used for rangeland irrigation. The water, however, has a high sodium adsorption ratio, which can result in severe deterioration of soil permeability with repeated irrigation. The St. Cloud zeolites exhibit a low selectivity of Na+ over Ca2+ (Vanselow selectivity coefficients of 0.26 and usable Na+ exchange capacity of 0.1?meq/g) at the ionic strength of Na+-laden CBM waters (0.035?M). Nevertheless, given the availability and low cost of natural zeolites, ion exchange experiments were conducted using packed columns to estimate a treatment cost. The operation and maintenance cost of the zeolite system was estimated to be about $3 per barrel (one barrel = 159 liters) compared with $0.75–$4/bbl for deep well injection (primary management practice) and $0.06–$0.11/bbl for soil amendment. Based on these preliminary experiments, it is evident that the ion exchange process for Na+ removal, with natural zeolites as the media, is not economical due to the low sodium selectivity.     

Performance-Based Optimization of Land and Water Resources within Irrigation Schemes. II: Application

The area and water allocation model which uses simulation–optimization technique for optimum allocation of land and water resources to different crops cultivated in different allocation units of the irrigation scheme was modified to include both productivity and equity in the process of developing the allocation plans for optimum productivity and/or maximum equity. This paper illustrates the potential of this approach with the help of a case study on Nazare medium irrigation scheme in India. The allocation plans were developed for optimization of different performance parameters (productivity and equity) for different management strategies based on irrigation amount and irrigation interval and cropping distribution strategies of free and fixed cropping. The results indicated that the two performance objectives productivity and equity conflict with each other and in this case, equitable water distribution may be preferred over free water distribution at the cost of a small loss in productivity. Though these results relate to one case study, they show the value of the approach of incorporating productivity and equity in the allocation process with the help of the simulation-optimization model described in the companion paper.     

Effects of Different Levels of Irrigation Water Salinity and Leaching on Yield and Yield Components of Wheat in an Arid Region

Soil salinity is a major environmental factor limiting the productivity of agricultural lands. To determine the effects of irrigation water salinity and leaching on soil salinity and consequently wheat yield, a field experiment was conducted on a silty clay soil, a typical soil of Rudasht region, Isfahan province, Iran, with three irrigation water salinity levels of 2, 8, and 12?dS/m with/without leaching levels of 4, 19, and 32% with two different irrigation water managements, using factorial design with four replications for each treatment. The results showed that as the irrigation water salinity and consequently soil salinity increases, the yield components such as grain yield, straw yield, 1,000-grain weight, crop height, spike length, and leaf area index decreases significantly. Leaching caused the yield components to increase significantly. An increase in seed protein percentage was noted as the salinity of irrigation water increased. The interaction effects of irrigation management and leaching on yield and yield components was significant. The results of best fit line to relative yield data versus soil ECe showed that the parameters of the above linear relation are site specific, and there is no significant difference between the parameters obtained in this study as compared to the other researchers’ results and the study validates the established relationships between wheat yield and salinity obtained by other researchers. The recycled drainage water could be used in combination with less saline river water as an alternative and less expensive irrigation water to grow salt-tolerant crops such as wheat, to produce profitable yield and to improve the agricultural economy of arid land regions.     

Integrated Agro-Economic Approach to Deficit Irrigation on Lettuce Crops in Sicily (Italy)

The effect of four different irrigation levels on the marketable yield and economic return of summer-growth lettuce was evaluated during 2005 and 2006 in Eastern Sicily, Italy. The viability of deficit irrigation was evaluated by estimating optimum applied water levels. Actual evapotranspiration (ETa) was estimated by combining pan evaporation measures and the Penman–Monteith approach (ET0-PM). The highest marketable yield of lettuce was recorded for plots receiving 100% ET0-PM. For deficit irrigated plots, reductions in crop production were ascribed to a decrease in lettuce weight. Crop coefficients equal to 1 determined maximum crop production values. Crop water use efficiency was maximum at a 100% ET0-PM level of water applied, corresponding to yield of 0.3?t?ha?1?mm?1. Irrigation water use efficiency reached its maximum at a 40% ET0-PM level, with values of 0.54 and 0.44?t?ha?1?mm?1 during 2005 and 2006, respectively. Water applied and marketable yield of lettuce showed a significant quadratic relationship. Cost functions had a quadratic form during 2005 and a linear form during 2006. In the land-limiting condition the optimal economic levels fit the agronomic ones well. In the water-limiting condition, ranges of water deficit of 15–44% and 74–94% were as profitable as full irrigation, thus contributing to appreciable water savings.     

Set Sprinkler Irrigation and Its Cost

In this study, annual water application costs per unit area (ha) have been analyzed at the level of irrigation subunit in set sprinkler irrigation systems designed with pipes of different materials. In the cost, investment (pumping, pipes, sprinklers, ditches), energy, labor, maintenance, and water costs have been considered. Four systems were studied: one with buried pipes, in a permanent solid-set system, using: (a) polyvinyl chloride with buried pipes (PVCb), and three with pipes on the surface in surface solid-set systems, using (b) polyvinyl chloride pipes, (c) polyethylene pipes, and (d) aluminum pipes. The correct selection of the irrigation subunit size and shape can lead to a significant decrease in cost. The most economic irrigation subunits, among the four systems studied, were those formed by four laterals and a number of sprinklers per lateral of 10, 9, and 6 at 12?m×12?m, 12?m×18?m, and 18?m×18?m spacing, respectively. The most influential factor on the annual water application cost was spacing. Considering total annual cost, water cost was the most important, followed by investment and energy. Among the analyzed systems, the permanent system using PVCb produced the lowest annual water application cost per unit area.     

Evaluation of the Water Delivery Performance of the Menemen Left Bank Irrigation System Using Variables Measured On-Site

This study determines the water delivery performance at secondary and tertiary canal level of the Menemen Left Bank Irrigation system, an open canal irrigation system located in Turkey, for the irrigation seasons of the years 2005–2007. At secondary canal level, water supply ratio was used, and at tertiary level, the indicators of adequacy, efficiency, dependability, and equity were used. In calculating these indicators in this study, the amounts of water diverted to the canals, efficiency of water conveyance, and of water application were measured. Of these indicators, the water supply ratio was determined for the secondary canal, and the other indicators were determined for a total of six selected tertiary canals at the head, middle, and lower end of the secondary. At secondary level, the water supply ratios obtained to total irrigation water requirements for the months of July and August, when requirement for irrigation water is at a maximum, was determined to be less than one, while the water supply ratios obtained to net irrigation water requirement was found to be more than one. With regard to water delivery performance at tertiary level, adequacy, efficiency, dependability, and equity were found to be poor for each of the three years of the study, with efficiency rising to “fair” level only in 2005. In order to raise the water delivery performance of the system, it is necessary to reduce water conveyance losses to increase the water application efficiency, to prepare water distribution plans which take in tertiary canals, and to measure and monitor the water diverted to the canals.     

Regional Water Management Modeling for Decision Support in Irrigated Agriculture

Efficient water management is one of the key elements in successful operation of irrigation schemes in arid and semiarid regions. An integrated water management model was developed by combining an unsaturated flow model and a groundwater simulation model. These combined models serve as a tool for decision making in irrigation water management to maintain the water tables at a safe depth. The integrated model was applied on a regional scale in Sirsa Irrigation Circle, covering about a 0.42 million ha area in the northwestern part of Haryana, India, which is faced with serious waterlogging and salinity problems in areas underlain with saline ground irrigated by the canal network. The model was calibrated using the agrohydrologic data for the period 1977–1981 and validated for the period 1982–1990 by keeping the calibrating parameters unchanged. The model was used to study the long-term impact of two water management interventions related to the canal irrigation system—change in pricing system of irrigation water, and water supply according to demand—on the extent of waterlogging risk. Both of these strategies, if implemented, would considerably reduce aquifer recharge and consequently waterlogging risk, compared to the existing practice. The water supply according to demand strategy was slightly more effective in reducing aquifer recharge than the water pricing intervention. The implementation of the proposed water pricing policy would pose no problem in fitting into the existing irrigation system, and thus it would be easier to implement, compared to the water supply according to demand strategy, when taking technical, financial, and social considerations into account.     

Expanding Disk Rain Sensor Performance and Potential Irrigation Water Savings

Rain sensors (RSs) appear to be a useful tool for water conservation at a relatively low cost. However, little evidence related to RS performance and/or reliability exists. The objectives of this experiment were to: (1) evaluate two RS types with respect to the following: Accuracy of their set point, number of irrigation cycles bypassed, and duration in bypass mode; (2) quantify the amount of water that RSs could save; and (3) estimate their payback period. Mini-click (MC) and wireless rain-click (WL) rain sensor models were monitored. For the WL treatment, the dry-out ventilation windows were set half open, and for the MC treatments, rainfall set points of 3, 13, and 25?mm were established. On average, all treatments responded close to their set points with the WL, 3?mm MC, 13?mm MC, and 25?mm MC treatments averaging 1.4, 3.4, 10.0, and 24.5?mm, respectively. However, some replicates showed variable behavior. The number of times that these sensors shut off irrigation (81, 43, 30, and 8 times, respectively) was inversely proportional to the magnitude of their set point, with potential water savings following a similar trend. Where water costs exceed $0.53 per cubic meter ($2.00 per thousand gallons), the payback period is less than a year for WL and MCs set at 13?mm or less.     

Farmers’ Adaptation and Regional Land-Use Changes in Irrigation Systems under Fluctuating Water Supply, South India

In closing river basins where nearly all available water is committed to existing uses, downstream irrigation projects are expected to experience water shortages more frequently. Understanding the scope for resilience and adaptation of large surface irrigation systems is vital to the development of management strategies designed to mitigate the impact of river basin closure on food production and the livelihoods of farmers. A multilevel analysis (farm-level surveys and regional assessment through remote-sensing techniques and statistics) of the dynamics of irrigation and land use in the Nagarjuna Sagar project (South India) in times of changing water availability (2000–2006) highlights that during low-flow years, there is large-scale adoption of rainfed or supplementary irrigated crops that have lower land productivity but higher water productivity, and that a large fraction of land is fallowed. Cropping pattern changes during the drought reveal short-term coping strategies rather than long-term evolutions: after the shock, farmers reverted to their usual cropping patterns during years with adequate canal supplies. For the sequence of water supply fluctuations observed from 2000 to 2006, the Nagarjuna Sagar irrigation system shows a high level of sensitivity to short-term perturbations, but long-term resilience if flows recover. Management strategies accounting for local-level adaptability will be necessary to mitigate the impacts of low-flow years but there is scope for improvement of the performance of the system.     

General Irrigation Planning Performance of Water User Associations in the Gediz Basin in Turkey

In this study, an evaluation has been made of the realization level of the planned targets in irrigation planning for all of the 13 water user associations (WUAs) of the Gediz Basin. This evaluation was made according to six performance indicators: level of realization of irrigation ratios, level of realization of crop pattern, dependability, adequacy, efficiency, and equity for the years 1999–2002. Seven associations were successful in irrigation ratio realization, and four were successful in crop pattern. Failure of other WUAs can be reduced by collecting farmers’ declarations and evaluating them with greater care and sensitivity. Water delivery in the general irrigation plan was found to be poor with regard to dependability and equity, and good with regard to the indicators of adequacy (except in the year 2001) and efficiency. In order to improve dependability, the period when water is diverted from the source and the period when water is needed must coincide completely. In order to improve equity, delivery of water to WUAs must be carried out taking account of water requirements predicted in the general irrigation plan. When these two indicators are improved, adequacy and efficiency will improve also.     

Economics of Furrow Irrigation under Partial Infiltration Information

The effects of partial infiltration and furrow geometry information on furrow irrigation design and economic return to water were quantified on a single furrow (reference furrow) and field-wide (10-furrow set) basis using a kinematic-wave furrow irrigation model in conjunction with an economic optimization model. A furrow sampled at 10 locations was assumed to represent the actual field condition. Subsamples were randomly drawn from the 10 samples and return to water was maximized. These suboptimal designs were applied to the actual furrows and monetary loss due to lack of information was simulated. The monetary loss was less for furrow irrigation designs having high inflow rates ($0.38∕furrow, $17∕ha) than for the low inflow rates ($2.27∕furrow, $100∕ha). Average loss decreased from $31∕ha ($0.71∕furrow) to $0∕ha in the case of the reference furrow, and from $1.0∕furrow ($44∕ha) to $0.3∕furrow ($13∕ha) in the case of the 10-furrow set for the samples sizes of 1 and 10, respectively.     

Growth and Evapotranspiration of Okra (Abelmoschus Esculentus L.) as Influenced by Salinity of Irrigation Water

The effects of irrigation water salinity on growth, yield, and water consumption of okra was investigated with a pot experiment. For this purpose, five irrigation water salinity levels with electrical conductivities of 1.5, 2.5, 3.5, 5.0, and 7.0?dS/m and tap water as a control treatment were used in a randomized design with five replications. Irrigation practices were realized by considering the weight of each pot. Threshold soil salinity and slope values of the yield response to soil salinity level were determined to be 3.48?dS/m and 4.2%, respectively, for fruit yield, 4.24?dS/m and 7.0% for vegetative dry weight, and 6.0?dS/m and 7.9% for root dry weight. The results revealed that okra was moderately tolerant to salinity. Increasing soil salinity levels caused significant decreases in plant water consumption. Plant water consumption decreased by 2.43% per unit increase in soil salinity. Plant coefficient (Ky) was 1.26. Saline irrigation water treatments altered Cl, Mg, Ca, and Na accumulations in leaves, whereas only Na accumulation in fruits was observed.     

Irrigation Performance using Hydrological and Remote Sensing Modeling

Development of water saving measures requires a thorough understanding of the water balance. Irrigation performance and water accounting are useful tools to assess water use and related productivity. Remote sensing and a hydrological model were applied to an irrigation project in western Turkey to estimate the water balance to support water use and productivity analyses. Remote sensing techniques can produce high spatial coverage of important terms in the water balance for large areas, but at the cost of a rather sparse temporal resolution. Hydrological models can produce all the terms of the water balance at a high temporal, but low spatial resolution. Actual evapotranspiration for an irrigated area in western Turkey was calculated using the surface energy balance algorithm for land (SEBAL) remote sensing land algorithm for two Landsat images. The hydrological model soil-water-atmosphere-plant (SWAP) was setup to simulate the water balance for the same area, assuming a certain distribution in soil properties, planting dates and irrigation practices. A comparison between evapotranspiration determined from SEBAL and from SWAP was made and differences were minimized by adapting the distribution in planting date and irrigation practice. The optimized input data for SWAP were used to simulate all terms of the accumulated water balance for the entire irrigation project, and subsequently used to derive the irrigation performance indicators. The innovative methodology presented is attractive as it diminishes the need of field data and combines the strong points of remotely sensed techniques and hydrological models.     

Regional Alfalfa Yield, ETc, and Water Value in Western States

Alfalfa hay yield, yield-consumptive use ratio (Y∕ETc), and hay price across a range of rainfall and evapotranspiration conditions of the western states is evaluated to determine alfalfa hay water value or benefit. Included is a determination of long-term mean values and variability of yield, Y∕ETc ratios, and associated irrigation water values. These are compared with published hay water-use efficiencies, production, and water costs. Available rainfall, reference evapotranspiration ET0, hay yields, and prices for counties in Arizona (1987–1999), California (1998–1999), and Idaho (1993–1999) were used. Alfalfa hay Y∕ETc ratios decrease with increasing ETc, although their variability increases with increasing ETc. The greatest Y∕ETc ratios (16–17 kg∕ha-mm) and irrigation water values IW$ (IW$ = $2,800–$3,000∕ha-m), with relatively moderate variability, are associated with an irrigation water IW requirement of ～800 mm, reflecting a combination of relatively high hay values, ETc, and beneficial rain. Although this IW$ is twice that of water delivery prices below the California delta and is comparable with average municipal water costs of $4,000∕ha-m for large western cities, the average is nearly 1∕3.     

Effects of Magnetized Water and Irrigation Water Salinity on Soil Moisture Distribution in Trickle Irrigation

Magnetized water is obtained by passing water through a strong permanent magnet installed in or on a feed pipeline. This study was performed at Gorgan Agricultural and Natural Resources Research Center, Gorgan province, Iran, to investigate soil moisture distribution under trickle irrigation. Two main treatments of magnetic and nonmagnetic water and three subtreatments of irrigation water salts, including well water as a control, 200-ppm calcium carbonate, and 400-ppm calcium carbonate were used. The experiment was laid out with a complete randomized block design with three replications. Soil moisture distribution around the emitters were measured 24?h after irrigation during the 3-month irrigation period. The results showed that the mean soil moisture contents at depths of 0–20, 20–40, and 40–60?cm below the emitter for the magnetized irrigation water treatment were more than the nonmagnetized irrigation water treatment, and the differences were significant at the 5% level. The irrigation with magnetic water as compared with the nonmagnetic water increased soil moisture up to 7.5%, and this increase was significant at the 1% level. The effect of irrigation water salinity on soil moisture was significant. The highest soil moisture content was from the 400-ppm calcium carbonate subtreatment. The use of magnetized water for irrigation is recommended to save irrigation water.     

Water Management of Irrigated-Drained Fields in the Jordan Valley South of Lake Kinneret

The Jordan Valley is one of the primary regions for growing winter crops of fruit and vegetables in Israel and Jordan. Control of water management in these fields is obtained by solid-set irrigation systems and subsurface drainage. Detailed field observations were conducted at a location near the Jordan River, south of Lake Kinneret. Water table heights were measured by approximately 100?piezometers. An exiting wide spacing (160?m) subsurface drainage system was monitored and the total drainage discharge from this regional drainage system to Lake Kinneret was measured. Rainfall, irrigation, and evapotranspiration rates were measured and overall hydrological balance was conducted. The old irrigation method in the region was border irrigation with very high leaching fraction and poor irrigation efficiency. During the 1970s the irrigation method was changed to computer operated drip irrigation. The leaching fraction was reduced and irrigation efficiency increased. Reduction of the total drainage discharge to Lake Kinneret by a factor of about 10 was observed. Water table rise under hand moving sprinkler and soil-set drip irrigation methods were measured and compared for assessment of salinization of the root zone by upward movement of groundwater. The result indicates the strong effect of irrigation time interval on the extent of these rises. The effect of irrigation mode on the extent of water table rises was measured at the field by comparing that under hand moving sprinkler irrigation to that under water solid set drip method. This effect depends, among other variables, on the irrigation time interval, a fact which complicates prediction of water table rise under different irrigation practices. These field results support previous theoretical analysis by the writers and highlighted the interrelationship between irrigation practice and drainage design. The effect of water table drawdown towards the Jordan River was monitored and found to be about 4.6%. The strong influence of the Jordan River on water table height at the drained field is magnified by the existence of sandy layers in the soil profile. This observed gradient may be used for the estimation of lateral seepage flow from the irrigated agricultural field towards the adjacent Jordan River. This study provides a useful source of data for future studies in similar situations.