Assessment of alternative water management options for irrigated agriculture

A simulation study on alternative water management strategies was carried out for Sirsa Irrigation Circle in Haryana, covering an area of about 4800 km². Results showed that crop evapotranspiration and soil salinity development under reduction in canal water supply and increase in groundwater use, are largely influenced by the amount and distribution of rainfall. Reduction in canal water supply by 25% during the rainy season is unlikely to have any adverse effect on the salinity development in the study area. Reduction in crop evapotranspiration due to decreased canal water supply can partly be compensated by the increase in groundwater use. Leaching of salts due to monsoon rains in the study area shows that groundwater of even relatively poor quality can be used for irrigation without excessive long-term build up of soil salinity under deep groundwater depth conditions. However, increased groundwater extraction without associated actions will not be very effective to solve the problem of rising groundwater levels.     

The resource potential of in-situ shallow ground water use in irrigated agriculture: a review

Shallow ground water is a resource that is routinely overlooked when water management alternatives are being considered in irrigated agriculture. Even though it has the potential to provide significant quantities of water for crop use under the proper conditions and management. Crop water use from shallow groundwater is affected by soil water flux, crop rooting characteristics, crop salt tolerance, presence of a drainage system, and irrigation system type and management. This paper reviews these factors in detail and presents data quantifying crop use from shallow ground, and describes the existing state of the art with regard to crop management in the presence of shallow ground water. The existing data are used to determine whether in-situ crop water use from shallow ground water is suitable for a given situation. The suggested methodology uses ratios of ground water electrical conductivity to the Maas–Hoffman yield loss threshold values, the day to plant maturity relative to plant growth period, and the maximum rooting depth relative to the nearly saturated zone. The review demonstrates that for in-situ use to be feasible there has to be good quality ground water relative to crop salt tolerance available for an extended period of time. Shallow ground water availability is one area that can be managed to some extent. Crop selection will be the primary determinant in the other ratios.     

Assessment of suspended solids dynamics and their effect in the irrigation networks in the Northern Jordan Valley

This study aims to assess the suspended solids dynamics of the irrigation water, through total Suspended Solids (TSS) measures and field observations. Assessment is conducted along the distribution system in the Northern Jordan Valley. This study followed the water’s TSS conditions in the study area along its travel in King Abdullah Canal (KAC), in the pumping station (with all of its components) and in the delivery networks from the pumping station up to the farm units. TSS of the water in KAC fluctuates temporally and spatially. Pumping stations components performance with respect to TSS such as the bar rack, the static and the traveling screens, the settling basins and the well were evaluated. The design of settling basins showed acceptable specifications of the existing structure; however, management and operation conditions are the main concerns affecting their performance. This study showed the screens work with low efficiency because of operation faults and lack of maintenance especially for the traveling screen. Distribution network affects adversely the water’s TSS because of lack of flushing which enables sediments removal from the network, and prevents suspension process for the piled up sediments inside the network pipes. This study suggested using special points of low elevations in the network to flush piled up sediment out of the network. Finally, this study showed the flushing procedure the Jordan Valley Authority staff should take for cleaning the distribution network.     

Adjusting the irrigation water demand projection module to be viable in central Jordan Valley

In 2004, the Jordan National Water Master Plan (NWMP) was developed, which includes a number of water demand projection modules for assessing the existing water resources, and predicting demands on water for all uses; municipal, industrial, tourist and irrigation. The Irrigation Demand Module was tested with historical data and comparisons were made between the predicted demands as obtained by the module, and the recorded water use provided by relevant institutions. Serious imbalances appeared, totaling the irrigation water demands of more than 1.5 times the recorded irrigation water use. The purpose of this study was to verify the viability of the functional part of the Irrigation Demand Module, namely the Net Irrigation Requirements Calculator (NIR-Calculator) in terms of functions, factors, and data used for the calculations. Results show that the original NIR-Calculator overestimated the values of NIR in the initial growth stage, Kc_i, by almost 55 %, because Cuenca Formula is used in the original version to calculate the initial crop coefficient, while FAO-56 Formula is used in the modified version. When taking the Jordan climatic characteristic into consideration, the original NIR-Calculator underestimated the values of the mid growth stage crop coefficient, Kc_m, by 1.7?C3.5 %, as well as the values of the end growth stage crop coefficient, Kc_e, by 2.2?C8.0 %. The original NIR-Calculator overestimated the effective rainfall by 66.5, 44.8 and 34 % for dry, medium and wet scenarios, respectively. The NIR values obtained by the original NIR-Calculator differed than the modified NIR-Calculator by 5.2, 6.2 and 8.6 % for dry, medium and wet scenarios respectively. Finally, the irrigation demand volume for Deir Ala area obtained by the original NIR-Calculator differed than the modified NIR-Calculator by 2.0, 3.5 and 9.3 % for dry, medium and wet scenarios respectively. In conclusion, although there is a difference between these two versions of the NIR-Calculator, this difference is not enough to cause the 1.5 imbalance in the Irrigation Demand Module. This imbalance can??t be attributed only to the NIR-Calculator and further investigation is required to determine why the imbalance exists.     

Impact of crop rotation and minimum tillage on water use efficiency of irrigated cotton in a Vertisol

Crop water use efficiency of irrigated cotton was hypothesized to be improved by a combination of minimum tillage and sowing a wheat (Triticum aestivum L.) rotation crop. This hypothesis was evaluated in a Vertisol near Narrabri, Australia from 1997 to 2003. The experimental treatments were: continuous cotton sown after conventional or minimum tillage and minimum-tilled cotton–wheat. Soil water content was measured with a neutron moisture meter, and runoff with trapezoidal flumes. Application efficiency of irrigation water was estimated as the amount of infiltrated water/total amount applied. Plant available water was estimated using the maximum and minimum soil water storage during the growing season. Evapotranspiration was estimated with the water balance method using measured and simulated soil water data. Seasonal evapotranspiration was partitioned into that coming from rainfall, irrigation and stored soil water. Crop water use efficiency was calculated as cotton lint yield per hectare/seasonal evapotranspiration. Rotation of cotton with wheat and minimum tillage improved water use efficiency in some years and application efficiency in all years. Average seasonal evapotranspiration was higher with minimum tillage than with conventional tillage. In years when cotton was sown in all plots, average cotton crop water use efficiencies were 0.23, 0.23 and 0.22 kg (lint)/m³ for minimum-tilled cotton–wheat and continuous cotton, and conventionally tilled continuous cotton, respectively. In-season rainfall efficiency, transpiration and soil evaporation were unaffected by cropping system.     

Increasing productivity in irrigated agriculture: Agronomic constraints and hydrological realities

Irrigation is widely criticised as a profligate and wasteful user of water, especially in watershort areas. Improvements to irrigation management are proposed as a way of increasing agricultural production and reducing the demand for water. The terminology for this debate is often flawed, failing to clarify the actual disposition of water used in irrigation into evaporation, transpiration, and return flows that may, depending on local conditions, be recoverable. Once the various flows are properly identified, the existing literature suggests that the scope for saving consumptive use of water through advanced irrigation technologies is often limited. Further, the interactions between evaporation and transpiration, and transpiration and crop yield are, once reasonable levels of agricultural practices are in place, largely linear—so that increases in yield are directly and linearly correlated with increases in the consumption of water. Opportunities to improve the performance of irrigation systems undoubtedly exist, but are increasingly difficult to achieve, and rarely of the magnitude suggested in popular debate.     

Modeling a Rotation Supply System in a Pilot Pressurized Irrigation Network in the Jordan Valley, Jordan

Many farmers in the Jordan Valley have switchedfrom traditional surface irrigationto pressurized irrigation systems. Inorder for these pressurized irrigationmethods to be effective, farmers must have adequate flow andpressure at each FarmTurnout Assembly (FTA). No on-demandirrigation concept has yet been implemented inthe Jordan Valley, and the rotation concept is still in use today. The JordanValley Authority (JVA) is the agency responsiblefor the distribution of water to farmers in the Valley. JVA engineers wereused to implement the irrigation rotationschedule, without any attention being paid to itseffect on the pressure in the network. Using MS Excel, a computer spreadsheet model was createdto examine the effect of selected rotation on thepressure in the network. This model was called theTurnout Pressure Simulation Program (TPSP).The TPSP model was used to map and identifyfarms that will incur pressure problems with any of the selected rotation schedules. This modelwas tested in the northern part of a pilotpressurized irrigation network known as TO2,and included 131 irrigated farm units (400 ha)located in Adassiyeh at the northern end of the Jordan Valley. The TPSP model was also usedto study illegal openings and the effect of these on the pressure in the network. The effect of four, eight, and 12 illegal openings was studied for a selectedrotation schedule, and an average reduction in pressure of 12%, 30%, and 44% was noted compared to when there were no illegal openings.     

叶城县农村水价改革中阶梯式水价的应用

本文对叶城县农村供水基本情况作了介绍,对实施阶梯性水价的必要性进行了分析,提出了农村水价的改革思路和改革方案,并对阶梯式水价改革方案的实施进行了探讨.     

Building a climate resilient farm: A risk based approach for understanding water, energy and emissions in irrigated agriculture

The links between water application, energy consumption and emissions are complex in irrigated agriculture. There is a need to ensure that water and energy use is closely considered in future industry planning and development to provide practical options for adaptation and to build resilience at the farm level. There is currently limited data available regarding the uncertainty and sensitivity associated with water application and energy consumption in irrigated crop production in Australia. This paper examines water application and energy consumption relationships for different irrigation systems, and the ways in which the uncertainty of different parameters impacts on these relationships and associated emissions for actual farms. This analysis was undertaken by examining the current water and energy patterns of crop production at actual farms in two irrigated areas of Australia (one using surface water and the other groundwater), and then modelling the risk/uncertainty and sensitivity associated with the link between water and energy consumption at the farm scale. Results showed that conversions from gravity to pressurised irrigation methods reduced water application, but there was a simultaneous increase in energy consumption in surface irrigation areas. In groundwater irrigated areas, the opposite is true; the use of pressurised irrigation methods can reduce water application and energy consumption by enhancing water use efficiency. Risk and uncertainty analysis quantified the range of water and energy use that might be expected for a given irrigation method for each farm. Sensitivity analysis revealed the contribution of climatic (evapotranspiration and rainfall) and technical factors (irrigation system efficiency, pump efficiency, suction and discharge head) impacting the uncertainty and the model output and water-energy system performance in general. Flood irrigation systems were generally associated with greater uncertainty than pressurised systems. To enhance resilience at the farm level, the optimum situation envisaged an irrigation system that minimises water and energy consumption and greenhouse gas emissions. Where surface water is used, well designed and managed flood irrigation systems will minimise the operating energy and carbon equivalent emissions. Where groundwater is the dominant use, the optimum system is a well designed and managed pressurised system operating at the lowest discharge pressure possible that will still allow for efficient irrigation. The findings might be useful for farm level risk mitigation strategies in surface and groundwater systems, and for aiding adaptation to climate change.     

Drainable surplus assessment in irrigated agriculture: field application of the groundwater approach

To assess the drainable surplus of an irrigated area, a methodologybased on a groundwater-balance approach was developed and appliedin Schedule I-B of the Fourth Drainage Project near Faisalabad inPakistan. To determine the seasonal net recharge in this area, anumerical groundwater model was run in inverse mode. The data inputfor the model consisted of the geometry of the aquifer system, theaquifer parameters, and historical watertable elevations. The seasonalnet recharge values, calculated from the individual recharge anddischarge components, were tuned with the results of the inversemodelling. The advantage of such an integrated approach is that allthese components are linked. The design net recharge was estimatedfrom the historical net recharge of the wettest monsoon in the studyperiod. Its rainfall recharge values were then substituted for those of adesign monsoon. In this substitution procedure, the rainfall rechargemethodology and parameters were adopted from the tuning procedure.From this design net recharge, estimates could be made of the requireddrainable surplus, with and without drainage simulation.     

Reuse of drainage water from irrigated areas

Increasing competition for water of good quality and the expectation that at least half of the required increase in food production in the near-future decades must come from the world's irrigated land requires to produce more food by converting more of the diverted water into food. Reuse of the non-consumed fraction ('drainage water') of the irrigation water already diverted is a proven but risky option for better fresh water management. This paper presents an overview of different options for reuse of drainage water and guidelines for its safe use. Criteria for maximum irrigation water salinity to prevent soil deterioration and crop yield reduction, for the maximum concentration of toxic substances and limits for bacteriological water quality are given. Examples of sustainable reuse of drainage water in Egypt, India and the USA are presented. The usefullness of simulation models for the analysis of regional water and salt balances is demonstrated.     

Modeling shallow water table evaporation in irrigated regions

Groundwater discharge through evaporation due to a shallow water table can be an important component of a regional scale water balance. Modeling this phenomenon in irrigated regions where soil moisture varies on short time scales is most accurately accomplished using variably saturated modeling codes. However, the computational demands of these models limit their application to field scale problems. The MODFLOW groundwater modeling code is applicable to regional scale problems and it has an evapotranspiration package that can be used to estimate this form of discharge, however, the use of time-invariant parameters in this module result in evaporation rates that are a function of water table depth only. This paper presents a calibration and validation of the previously developed MOD-HMS model code using lysimeter data. The model is then used to illustrate the dependence of bare soil evaporation rates on water table depth and soil moisture conditions. Finally, an approach for estimating the time varying parameters for the MODFLOW evapotranspiration package using a 1-D variably saturated MOD-HMS model is presented.     

Efficiency differentials in the traditional agriculture of Northern Nigeria

It is generally accepted that farmers operating in traditional agricultural systems are highly efficient, given the resources and technology available to them. This has led to farm policies in third world countries which place a high emphasis on capital investments.This paper uses a frontier production function analysis to generate firm specific efficiency indices for traditional farms in three different areas in northern Nigeria. Computed indices are then employed in identifying both inter- and intra-area efficiency differentials. The relationships between technical efficiency and commonly used farm performance measures are also examined.The results indicate that efficiency scores range between 0·67 and 1·00. This implies that least efficient farmers could have obtained gross value of output 24–36% above their actual output. Thus, the results reported in this paper are not in total support of the conventional belief that no increase in traditional agricultural output is possible by a more efficient use of factors at the disposal of farmers. One implication of these findings is that extension programmes based on the experience of more successful farmers, even with traditional practice, can yield modest dividends.     

Evaluation of water management systems in a tubewell irrigated farm

Land development, improved systems of irrigation and drainage, and proper irrigation scheduling are becoming more and more important for the success of command area development of the various major and minor irrigation schemes. For realistic planning and execution of such programmes or for improving existing ones, a systematic evaluation of the various components of the existing systems would be necessary but is invariably lacking. This paper presents an attempt made in this direction at C.S.S.R.I. farm, Karnal (India) to evaluate the integrated effect of water management technology on the efficiency of the irrigation system. The parameters selected for evaluation were the efficiencies of pumping, conveyance and field application. Besides these three parameters, water use efficiency, an index of crop production per unit of water applied, was also evaluated.Investigations revealed that pumping efficiency for electrically driven centrifugal pumps was about 52% and the corresponding value for diesel engine run pumps sets was 30%. The conveyance efficiency in the study area was as high as 93% because the seepage loss in the field channels laid in the alkali soils of the study area was only 7%. The field layout for water application in the study area consisted of long, narrow borders. The water application efficiency for this system was 58% for a wheat crop and 42% for rice. The overall system efficiency for wheat crops was observed to be 54% as against a value of 39% for rice.The observed average total water requirements and water use efficiencies for wheat were 46 cm and 70 kg/ha cm^?1 and for rice 150 cm and 46 kg/ha cm^?1, respectively. At these efficiencies, it was also noted that a cavity tubewell would command an area of 4.5 ha, with rice and wheat as the principal crop rotation.From this study, it can be inferred that reasonably high irrigation system efficiencies (54% as against the national average of about 30%) are possible with good water management at farm level.     

Field evaluation of sand-ditch water harvesting technique in Jordan

Water harvesting is viable alternatives for rainfed agricultural production in semiarid lands. A field experiment was conducted to evaluate the efficiency of a relatively new water harvesting technique, called sand ditch, for moisture and soil conservation. Twelve field plots of 10 m × 2 m were constructed in two adjacent fields having silt loam soils but varied in soil depth, 0.75 m and 2 m, and slope of 10% and 12%. A 130 L barrel was installed at the downslope end of the plots to collect water and sediments at the end of each rainstorm along the rainy season. Three types of treatments were used in duplicates (12 plots in total); sand-ditch plots in which a ditch of 2-m long, 1 m wide and 0.8 m deep was constructed in the middle of plots across the slope (2 in each field), two compacted plots and two plots covered with plastic mulch in addition to four control plots, 2 in each field. The total amount of runoff, sediment concentration, total infiltration and sediment loss for the experimental plots were measured or calculated after each storm during the winter season 2004/2005. Experimental results showed that sand-ditch technique significantly reduced runoff and sediment loss and increased infiltration and soil moisture compared to control or compacted plots. The overall average runoff and sediment reductions in the sand-ditch plots were 46% and 61% compared to control plots. Sediment losses from compacted plots were about 2.2 and 6 folds higher than control and sand-ditch plots, respectively making soil compaction unsuitable technique for rainfall harvesting under the current experimental and climatic conditions. Construction of sand ditch also increased the dry matter yield of native grass by an average of 62% and 40% in the two experimental fields compared to control.     

The water balance of irrigated forages in northern Victoria, Australia

Knowledge of the components of the water balance - evaporation, transpiration and deep drainage - would be beneficial for targeting productivity improvements for irrigated forages in northern Victoria. We aimed to estimate these components using a simple water balance and the dual crop coefficients provided in FAO-56. Soil water deficits from a field experiment, comparing the water use of six border-check and one spray irrigated forage system, agreed well with the modelled values, except for alfalfa where irrigation intake was restricted. About 85% of the water applied to perennial forages (perennial ryegrass/white clover, tall fescue/white clover and alfalfa) was used for transpiration, 10% for evaporation and 5% was lost as drainage below the root zone. Evaporation was highest from the double-cropped (oats/millet) system (30%) and was 5-25% of the water used by winter-growing annual pastures (Persian clover/Italian ryegrass and both border-check and spray irrigated subterranean clover/Italian ryegrass). The high proportion of water used as transpiration by the perennial forages was due to their high ground cover maintained throughout the year. When compared over similar seasonal conditions, actively growing forages used similar amounts of water, indicating that any increases in water productivity will be mainly due to higher production and/or to matching the growing season of the forage to periods of lower potential evapotranspiration.     

Increasing water productivity of irrigated crops under limited water supply at field scale

Borkhar district is located in an arid to semi-arid region in Iran and regularly faces widespread drought. Given current water scarcity, the limited available water should be used as efficient and productive as possible. To explore on-farm strategies which result in higher economic gains and water productivity (WP), a physically based agrohydrological model, Soil Water Atmosphere Plant (SWAP), was calibrated and validated using intensive measured data at eight selected farmer fields (wheat, fodder maize, sunflower and sugar beet) in the Borkhar district, Iran during the agricultural year 2004-2005. The WP values for the main crops were computed using the SWAP simulated water balance components, i.e. transpiration T, evapotranspiration ET, irrigation I, and the marketable yield Y_M in terms in terms of Y_MT⁻¹, Y_M ET⁻¹ and Y_M I⁻¹.The average WP, expressed as $ T⁻¹ (US $ m⁻³) was 0.19 for wheat, 0.5 for fodder maize, 0.06 for sunflower and 0.38 for sugar beet. This indicated that fodder maize provides the highest economic benefit in the Borkhar irrigation district. Soil evaporation caused the average WP values, expressed as Y_M ET⁻¹ (kg m⁻³), to be significantly lower than the average WP, expressed as Y_MT⁻¹, i.e. about 27% for wheat, 11% for fodder maize, 12% for sunflower and 0.18 for sugar beet. Furthermore, due to percolation from root zone and stored moisture content in the root zone, the average WP values, expressed as Y_MI⁻¹ (kg m⁻³), had a 24-42% reduction as compared with WP, expressed as Y_M ET⁻¹.The results indicated that during the limited water supply period, on-farm strategies like deficit irrigation scheduling and reduction of the cultivated area can result in higher economic gains. Improved irrigation practices in terms of irrigation timing and amount, increased WP in terms of Y_MI⁻¹ (kg m⁻³) by a factor of 1.5 for wheat and maize, 1.3 for sunflower and 1.1 for sugar beet. Under water shortage conditions, reduction of the cultivated area yielded higher water productivity values as compared to deficit irrigation.     

Evaluation of crop water stress index for LEPA irrigated corn

This study was designed to evaluate the crop water stress index (CWSI) for low-energy precision application (LEPA) irrigated corn (Zea mays L.) grown on slowly-permeable Pullman clay loam soil (fine, mixed, Torrertic Paleustoll) during the 1992 growing season at Bushland, Tex. The effects of six different irrigation levels (100%, 80%, 60%, 40%, 20%, and 0% replenishment of soil water depleted from the 1.5-m soil profile depth) on corn yields and the resulting CWSI were investigated. Irrigations were applied in 25 mm increments to maintain the soil water in the 100% treatment within 60–80% of the “plant extractable soil water” using LEPA technology, which wets alternate furrows only. The 1992 growing season was slightly wetter than normal. Thus, irrigation water use was less than normal, but the corn dry matter and grain yield were still significantly increased by irrigation. The yield, water use, and water use efficiency of fully irrigated corn were 1.246 kg/m², 786 mm, and 1.34 kg/m³, respectively. CWSI was calculated from measurements of infrared canopy temperatures, ambient air temperatures, and vapor pressure deficit values for the six irrigation levels. A “non-water-stressed baseline” equation for corn was developed using the diurnal infrared canopy temperature measurements as T _c–T _a = 1.06–2.56 VPD, where T _c was the canopy temperature (°C), Ta was the air temperature (°C) and VPD was the vapor pressure deficit (kPa). Trends in CWSI values were consistent with the soil water contents induced by the deficit irrigations. Both the dry matter and grain yields decreased with increased soil water deficit. Minimal yield reductions were observed at a threshold CWSI value of 0.33 or less for corn. The CWSI was useful for evaluating crop water stress in corn and should be a valuable tool to assist irrigation decision making together with soil water measurements and/or evapotranspiration models. Received: 19 May 1998