The Pros and Cons of Encouraging Shallow Groundwater Use through Controlled Drainage in a Salt-Impacted Irrigation Area

Encouraging shallow groundwater use through water table management or controlled drainage in irrigated areas can relief crop water stress under water shortage condition. But substituting fresh irrigation water with saline groundwater may speed up salinity buildup in the crop root zone, and consequently increase water use for salt leaching. With a proposed analytical model, this paper presents a case study demonstrating the effect of encouraging shallow groundwater use through controlled drainage on salt and water management in a semi-arid irrigation area in northwestern China. Based on the average rainfall condition, the model assumes that salt accumulates in the crop root zone due to irrigation and shallow groundwater use; till the average soil salinity reaches the crop tolerance level, leaching irrigation is performed and the drainage outlet is lowered to discharge the salt-laden leaching water. For the relatively salt tolerant crop–cotton in the study area, the predicted leaching cycle was as long as 751 days using the fresh water (with salinity of 0.5 g/L) irrigation only; it was shortened to 268 days when the water table depth was controlled at 2 m and 23% of the crop water requirement was contributed from the saline groundwater (with salinity of 4.43 g/L). The predicted leaching cycle was 140 days when the water table depth was controlled at 1.5 m and groundwater contribution was 41% of the crop water requirement; it was shortened to 119 days when the water table depth was controlled at 1.2 m and the groundwater contribution was 67% of the crop water requirements. So the benefit from encouraged shallow groundwater use through controlled drainage is obtained at the expense of shortened leaching cycle; but the shallow groundwater use by crops consists of a significant portion of crop water requirements, and the leaching cycle remains long enough to provide a time window for scheduled leaching in the off season of irrigation. Weighing the pros and cons of the encouraged shallow groundwater use may help plan irrigation and drainage practices to achieve higher water use efficiency in saline agricultural areas.     

作物需水量与灌溉制度模拟

从作物需水量的基本概念出发，以水量平衡原理为基础，建立了模拟农田根层土壤水循环的计算机模型-ISAREG.这一模型具有多种功能，可模拟根层土壤水分变化，评价给定的灌溉制度，计算作物需水量和灌溉需水量，也可用以制订多种供水限制条件下的优化灌溉制度．用望都灌溉试验站的小麦、玉米、棉花3种作物两年的试验观测资料对上述模型进行了验证．     

An application of linear programming to determine optimal systems for rainwater management: An economic view

Two decision models, one for determining optimal systems for rainwater management and the other for allocating additional water supplies from managed rainfall in conjunction with irrigation water, are formulated. The application of a rainwater management model to the command and to a watercourse, decides the minimum cost activities to manage rainwater. The output from the first model is used as the input in the second model which optimally allocates water to competing crops. It has been shown that 80% of rainwater could be managed economically in rice fields and in storage underground through artificial recharge. Optimal allocation of managed rainwater in conjunction with irrigation water increases the income of the project area to the extent of 14%.List of symbols AER Total available energy kWh - B _max Maximized value of the objective function, Rs - C _W Cost of canal water, Rs/10³ m³ - C _i Cost of managing rainwater through activityi, Rs/10³/m³ - C _min Minimized cost of managing surplus rainwater, Rs - C _RF Average cost of managed rainwater through activityi, Rs/10³ m³ - E _i Energy consumption in rainwater management activityi, kWh/10³ m³ (only energy required for pumping water is considered) - FLS Available capacity for fallow land storage, 10³ m³ - FPS Total storage in lined and unlined farm ponds, 10³ m³ - GWR Runoff diversion for artificial recharge through inverted tubewells, 10³ m³ - i A suffix for management activities having values 1,2,3,..., - j Crop index having values 1,2,3,..., - k Index for crop season, 1=kharif (summer) and 2=rabi(winter) - MRF Maximum rainfall surplus (runoff) available for management. (Runoff value at a 5-year return period was adopted) - P _j Income from crop activityj, Rs/ha - RFL Storage in fallow alkali land, 10³ m³ - RFS Storage in rice fields up to various depths, 10³ m³ - RWM _i Volume of rainwater managed through activityi, 10³ m³ - VCW Volume of canal water, 10³ m³ - VGW Volume of ground water, 10³ m³ - X _j Area under cropj, ha.     

Pond and Irrigation Model (PIM): a Tool for Simultaneously Evaluating Pond Water Availability and Crop Irrigation Demand

Agricultural ponds are an important alternative source of water for crop irrigation to conserve surface and ground water resources. In recent years more such ponds have been constructed in Mississippi and around the world. There is currently, however, a lack of a tool to simultaneously estimate crop irrigation demand and pond water availability. In this study, a Pond-Irrigation Model (PIM) was developed to meet this need using STELLA (Structural Thinking, Experiential Learning Laboratory with Animation) software. PIM simulated crop land and agricultural pond hydrological processes such as surface runoff, soil drainage, and evapotranspiration as well as crop irrigation demand and pond water availability. More importantly, PIM was able to decide when to conduct crop irrigation based on management allowable depletion (MAD) root zone soil water content and to determine optimal ratios of agricultural pond size to crop land with sufficient pond water available for crop irrigation. As a case demonstration, the model was applied to concomitantly estimate row crops (i.e., corn, cotton, and soybeans) water irrigation demand and pond water availability in a farm located at East-central Mississippi. Simulations revealed that corn used more soil water for growth than soybeans, whereas soybeans needed more irrigation water than corn and occurred due to less rainwater available for soybeans growth. We also found that there was one time for corn, zero time for cotton, and two times for soybeans when the pond water level was drawn to near zero for irrigation from 2005 to 2014. PIM developed in this study is a useful tool for estimating crop irrigation demand and pond water availability simultaneously.     

Performance of Low Energy Water Application Device

Considering the overall farming situation in developing countries particularly India it has been observed that the available options of efficient irrigation technologies are unable to cover up small and marginal farm holders due to lack of the applicability and acceptability in terms of their needs, priorities and financial capabilities. This makes imperative to develop a substitute of existing technologies that could be cheap simple and less capital intensive as well as applicable for small farms. This paper discusses the performances of a low cost water and energy efficient device called LEWA which can be used in place of overhead impact sprinklers to irrigate field and row crops efficiently at small farms. LEWA can be operated at an operating pressure range 39 to 98 kPa at its nozzle head, with discharge rate 0.87–1.10 m³/h, and throw diameter 6–8 m. Since operating pressure at the nozzle head governs overall system pressure and reflects the total cost of the system, size of prime mover pump required and its operational cost; therefore the developed device holds greater promise in development of a cost effective water and energy efficient pressurized irrigation system for small and marginal farmers possessing small and fragmented land.     

膜下滴灌不同灌水定额及水氮耦合对打瓜耗水规律的影响

为研究不同灌水定额和不同施氮量对北疆打瓜耗水规律的影响,2016-2017年在新疆阿勒泰地区灌溉试验站陆续开展2 a大田打瓜灌水试验,讨论连续2 a不同灌水定额及水氮互作下打瓜耗水规律。2016年试验设置5个不同的灌水定额分别为300、375、450、525、600 m~3/hm~2。2017年设置3个不同灌水定额分别为300、450、600m~3/hm~2,3个不同施氮量分别为0、138、276 kg/hm~2,共9个处理。研究结果表明:不同灌水定额和水氮互作下打瓜旬均耗水量变化规律均呈先增大后减小变化规律;耗水量、耗水强度和果实膨大期的耗水模数随着灌水定额增加而呈"增大-平缓"态势;打瓜作物系数随灌水定额增加而增大,且在0. 360～0. 431间变化,其中600 m~3/hm~2灌水定额耗水量、耗水强度和作物系数最大;合适的水氮供给量有利于打瓜耗水模数、作物系数、耗水量和耗水强度增大,作物系数在0. 317～0. 445间变化;与其他生育阶段相比,不同灌水定额和水氮互作均在果实膨大期对打瓜耗水量、耗水强度和作物系数的影响最大。研究可为理解大田打瓜的耗水特性和当地打瓜节水高效生产提供依据。     

Water Pricing for Agricultural Production in the South of Iran

Appropriate water resource allocation in dry land area is very important for farm management. Although very few systems for water distribution have efficient pricing, water resources should be allocated so that the marginal cost equals the marginal value product of water for all uses and users. When the marginal values are not equal, it is always possible to find a reallocation of water that increases net social benefits. Microeconomic techniques used for estimating the value of water and determining farmers’ willingness to pay include: net-back analysis, hedonic models, and optimization models. The main objective of this study was to compare marginal value product of irrigation water applied to grow the selected crops in the southern Iran. We used net-back analysis to evaluate agricultural water value in the Hormozgan province (southern Iran). The empirical information is drawn from the agricultural service agencies and survey from farmer’s respondents. Data set is included quantity of output, prices, and costs of selected crops and water. The calculated net-back value for each product indicates the maximum ability to pay (MATP) or the shadow price of water used in irrigation. That is, if a farmer pays that amount for water he gets neither benefit nor loss. The results indicated that among selected crops, cucumber and lime had the highest return for water use. The most important management implication of this study is the reallocation of irrigation water according to the economic value of water in various crops.     

Role of Virtual Water in Optimizing Water Resources Management in Jordan

Role of virtual water (VW) in optimizing water resources management in Jordan, a far water-short country, was explored by calculating VW content of imported commodities and their costs. Feasibility of farming and water required to produce all crops growing in Jordan were evaluated using net return per unit volume of water and VW embedded in unit mass of production. The results of these analyses showed that there were regional differences in crop profitability and thus net return from unit volume of irrigation water. This was attributed to variations in agro-climatic zones punctuated by production and irrigation technologies and access to water resources. In this regard, opportunity cost of water should be considered when allocating water to different consumption sectors. Agricultural systems generating net profits less than an arbitrary limit of $1.0?m^?3 of irrigation water and producing yield at water use efficiency of 50?C60?m³?ton^?1 or more were viewed not feasible. The key challenge facing decision makers would be to ensure that the opportunity cost of water was incorporated into the analysis process when determining future cropping pattern. Such a cost of water should be combined with crop-embedded VW analysis and expected net return from unit volume of irrigation water. Therefore, water allocation mechanism (e.g. water market) need to be developed for more efficient water use than the commonly practiced farm quota. Optimization of the usage of the limited water resources can be envisaged by continuous imports of VW, especially that embedded in cereal, oil, meat, live animals and sugar. Appropriate amendment of water legislations and concerned institutions are encouraged to provide better guidelines to policy makers, water managers, extension and advisory services, water use associations and farmers. Optimization of water resources management could be based on contract farming to ensure that water allocation and cropping pattern respond to water scarcity. Furthermore, Jordan should concentrate on production and export of crops having low VW contents and high return per m³.     

Agricultural Multi-Water Source Allocation Model Based on Interval Two-Stage Stochastic Robust Programming under Uncertainty

Numerous uncertainties and complexities exist in the agricultural irrigation water allocation system, that must be considered in the optimization of water resources allocation. In this paper, an agricultural multi-water source allocation model, consisting of stochastic robust programming and two-stage random programming and introducing interval numbers and random variables to represent the uncertainties, was proposed for the optimization of irrigation water allocation in Jiamusi City of Heilongjiang Province, China. The model could optimize the water allocaton to different crops of groundwater and surface water. Then, the optimal target value and the optimal water allocation of different water sources distributed to different crops could be obtained. The model optimized the economic benefits and stability of the agricultural irrigation water allocation system via the introduction of a the penalty cost variable measurement to the objective function. The results revealed that the total water shortage changed from [18.6, 32.3]?×?10⁸ m³ to [15.7, 26.2]?×?10⁸ m³ at a risk level ω from zero to five, indicating that the water shortage decreased and the reliability improved in the agricultural irrigation water allocation system. Additionally, the net economic benefits of irrigation changed from [287.21, 357.86]?×?10⁸ yuan to [253.23, 301.32]?×?10⁸ yuan, indicating that the economic benefit difference was reduced. Therefore, the model can be used by decision makers to develop appropriate water distribution schemes based on the rational consideration of the economic benefit, stability and risk of the agricultural irrigation water allocation system.     

Simulation supported scenario analysis for water resources planning: a case study in northern Italy.

The work presents the results of a comprehensive modelling study of surface and groundwater resources in the Muzza-Bassa Lodigiana irrigation district, in Northern Italy. It assesses the impact of changes in land use and irrigation water availability on the distribution of crop water consumption in space and time, as well as on the groundwater resources. A distributed, integrated surface water-groundwater simulation system was implemented and applied to the study area. The system is based on the coupling of a conceptual vadose zone model with the groundwater model MODFLOW. To assess the impact of land use and irrigation water availability on water deficit for crops as well as on groundwater system in the area, a number of management scenarios were identified and compared with a base scenario, reflecting the present conditions. Changes in land use may alter significantly both total crop water requirement and aquifer recharge. Water supply is sufficient to meet demand under present conditions and, from the crop water use viewpoint, a reduction of water availability has a positive effect on the overall irrigation system efficiency; however, evapotranspiration deficit increases, concentrated in July and August, when it may be critical for maize crops.     

基于作物水分生产函数下的限额灌溉制度优化研究

通过对小麦、玉米、棉花等主要农作物的分阶段受旱试验，获得了三年的限额灌溉试验观测数据；采用非充分灌溉条件下的土壤水分运动理论分析试验数据，建立了限额灌溉条件下的作物蒸发蒸腾模型。结合试验数据分析水分亏缺对作物产量的影响，采用多元回归分析法求解水分生产函数模型参数。采用动态规划法研究了水资源不足条件下的限额灌溉制度的多阶段优化法。研究成果表明，在产量能达到充分灌溉条件下产量的90％的情况下，可节约灌溉用水40％，能为水资源极其短缺地区的农业高效用水提供有力的技术支撑。     

Reuse of wastewater effluent for irrigation in severely arid regions

Al‐Hassa oasis, with an estimated population of 750000, is one of the main agricultural areas in Saudi Arabia. The estimated present agricultural water consumption in the oasis is almost 419 × 10⁶ m³ per year and the water is mainly supplied from the aquifer systems in the oasis. The climate is severely arid and the groundwater resources are limited. A deficiency in irrigation water supplies would occur in the oasis, especially during the summer season, without the reuse of wastewater effluent. Alternative schemes were developed on the basis of climatic, irrigation method, crop, health and economic considerations for the potential reuse of wastewater effluent for irrigation purposes. The schemes suggested different alternatives for reuse of the untreated effluent or with various types of additional treatments needed to render the water free of health hazards and suitable for agricultural use. An expected average wastewqter effluent of about 32.2 × 10⁶ m³/year will be available for irrigation purposes. This will result in minimizing the mining of groundwater and in conserving the water resources in Al‐Hassa oasis.     

Optimizing Deficit Irrigation Scheduling Under Shallow Groundwater Conditions in Lower Reaches of Amu Darya River Basin

Water demand for irrigated agriculture is increasing against limited availability of fresh water resources in the lower reaches of the Amu Darya River e.g., Khorezm region of Uzbekistan. Future scenarios predict that Khorezm region will receive fewer water supplies due to climate change, transboundary conflicts and hence farmers have to achieve their yield targets with less water. We conducted a study and used AquaCrop model to develop the optimum and deficit irrigation schedule under shallow groundwater conditions (1.0–1.2 m) in the study region. Cotton being a strategic crop in the region was used for simulations. Capillary rise substantially contributes to crop-water requirements and is the key characteristic of the regional soils. However, AquaCrop does not simulate capillary rise contribution, thereby HYDRUS-1D model was used in this study for the quantification of capillary rise contribution. Alongside optimal irrigation schedule for cotton, deficit strategies were also derived in two ways: proportional reduction from each irrigation event (scenario-A) throughout the growth period as well as reduced water supply at specific crop growth stages (scenario-B). For scenario-A, 20, 40, 50 and 60 % of optimal water was deducted from each irrigation quota whereas for scenario-B irrigation events were knocked out at different crop growth stages (stage 1(emergence), stage 2 (vegetative), stage 3 (flowering) and stage 4 (yield formation and ripening)). For scenario-A, 0, 14, 30 and 48 % of yield reduction was observed respectively. During stress at the late crop development stage, a reduced water supply of 12 % resulted in a yield increase of 8 %. Conversely, during stress at the earlier crop development stage, yield loss was 17–18 %. During water stress at the late ripening stage, no yield loss was observed. Results of this study provide guidelines for policy makers to adopt irrigation schedule depending upon availability of irrigation water.     

地下水位下降对干旱区膜下滴灌棉花需水量的影响

膜下滴灌种植方式大面积在西北干旱地区推广应用,使得该区地下水得不到有效补给,地下水位出现大幅下降。水位下降使地下水对土壤水的顶托作用和潜水的蒸发作用减弱,对作物需水量产生一定影响。利用2008~2018年新疆巴音郭楞蒙古自治州国家重点灌溉试验站不同地下水位进行滴灌实验的有利条件,研究地下水位下降对干旱地区膜下滴灌棉花滴灌水量的影响,并使用Penman-Monteith公式计算地下水埋深7～8 m时膜下滴灌棉花的需水量。研究表明：地下水位下降致使干旱地区的膜下滴灌棉花高产的需水量上升;滴灌水的入渗能力具有随矿化度增加而增加的趋势,且适宜的含盐量对棉花的生长具有一定的协同作用;当地下水埋深大于6 m时,水位的进一步下降将不再促使膜下棉花的需水量进一步上升。     

冀中山前平原农灌用水与地下水承载力适应性状况

针对冀中太行山前平原浅层地下水严重超采与农林灌溉用水之间关系问题,应用地学的模数理念、水量均衡理论方法和MapGIS空间特征分析技术,建立了农灌用水与地下水承载力之间适应性状况评价方法及指标体系,以0.49km2剖分单元精度识别了冀中山前平原农林灌溉用水强度及其与浅层地下水可采资源量之间适应性状况。结果表明,冀中山前平原农林灌溉导致的"极严重不适应"或"严重不适应"状态是浅层地下水超采的主要原因,其中小麦等夏粮作物灌溉用水主导了这些农灌区地下水超采,蔬菜作物和耗水型果林灌溉开采对地下水的影响呈显著增加趋势,应重视这种非理性加剧影响因素。     

试论灌溉水经济价值与粮棉作物种植布局

本文以我国十大区域灌溉需求指数为切入点,灌溉水经济价值为主要研究内容,在系统整编2000~2005年四种主要农产品成本收益资料的基础上,采用扣除非水成本法计算得出了十大区域四种主要作物灌溉水经济价值,揭示了作物适应性种植的地域性特征和规律性,提出粮棉作物种植的优势地区、种植布局以及政策扶持和倾斜的品种,为粮棉种植决策和维护国家粮食安全提供水资源方面的科学依据。     

Optimal Agricultural Water Allocation for the Sustainable Development of Surface and Groundwater Resources

This paper presents a multiobjective linear program for the optimal allocation of water resources among various crops in a large canal command area of Pakistan. The available surface water in the canal cannot meet the net irrigation requirement (NIR) of various crops, which leads to the overexploitation of groundwater and causes salinity problems. Therefore, an optimal water allocation model was formulated using the simultaneous compromise constraint (SICCON) technique for the sustainable development of surface water and groundwater. Three (03) single objective functions (OFs) and a multiobjective function (MOF) were considered in this study. The MOF combines the single OFs by developing an arrangement among them to both maximize the satisfaction rate for surface water (SR_s) and net economic returns (NER) and minimize the salinity problems. The available surface water (AW) of 1531 Mm³ was allocated among various crops, i.e., wheat, cotton, sugarcane, rice, onion, and sunflower, using the SICCON technique, and the deficit was accounted for with groundwater reserves. The model results showed an average increase of 22% in SR_s and 7.2 million USD in NER_s from surface water allocation compared to the current water allocation practice. Moreover, the salinity levels of the allocated water exceed the threshold limits of onion, sugarcane, and rice crops in the current water allocation system and thereby negatively impact agricultural production. Hence, the model used in this study may support decision-makers in the optimal selection of different crops to be irrigated to maximize the SR_s and NER_s and minimize salinity problems.

     

Agronomic aspects and environmental impact of reusing marginal water in irrigation: a case study from Egypt.

Egypt produces approximately 2.4 million m3 of secondary treated wastewater (TWW) annually, used for irrigation directly or indirectly by blending with agricultural drainage water (BDW). The annual re-use of (BDW) is approximately 4 million m3. The safe and efficient use of marginal water (BDW and TWW) is a core objective of this study which has been operating from 1997 to date. After six growing seasons the main results can be summarized as follows: MAXIMIZING CROP PRODUCTION: TWW can be used for high production of oil crops (canola, soybean sunflower or maize) compared to fresh water, while BDW can be used for high production of tolerant crops (cotton and sugar beet). CROP QUALITY: using marginal water increases the concentration of elements (Pb, B, Ni, Co) in all crops but these elements were under critical levels (there were no toxicity hazards). It is better to use alternative irrigation with fresh water under a drip irrigation system to maximise crop production and minimise the adverse effects of such water in field crops quality. SOIL POLLUTION AND SALINITY BUILD UP: A drip irrigation system under alternative irrigation by fresh with TWW or BDW reduces salinity build up risks and the levels of elements (Pb, B, Ni, Co) in soil compared to re-use marginal water. SOIL PATHOGENS: Using marginal water slightly contaminated the soil with total faecal coliform (TFC), mites, shigella and salmonella. PLANT ANATOMY: No great changes in anatomical disturbance where induced in different structures of plants which were reduced at maturity stage. PRIMARY GUIDELINES FOR RE-USING MARGINAL WATER: From obtained results it can be recommended to use marginal water with salinity content ranged between 1.1 to 3.64dS/m, and elemental contents (Pb 3.0-3.51 ppm), (B 0.05-1.67 ppm), (Co 0.04-0.07 ppm), (Ni 0.08-0.15 ppm) for safe (field, vegetable and medicinal) crops production. REUSE BIO SOLIDS FOR CROP PRODUCTION: Sewage sludge produced from treated wastewater can be safely used by mixing with rice straw (1:1 w/w) for economic crop production and saving mineral fertilisers. GENERAL CONCLUSION: In the North Nile Delta, marginal water (especially BDW) can be safely used without significant negative impact on the environment, but there is a need for multi-disciplinary, long-term research to investigate irrigation with marginal water in terms of the environment, public health and agricultural productivity.     

再生水灌溉研究进展

从再生水灌溉对土壤、作物、地下水和土壤斥水性4个方面简述国内外再生水灌溉的发展概况和研究进展。已有研究表明：再生水灌溉对土壤肥力和土壤酶活性的影响尚未有定论;再生水对农作物生长的影响尚有分歧;再生水灌溉对地下水水质具有一定的影响,并显著影响地下水水环境;长期的再生水灌溉会引发土壤斥水性的产生,且土壤斥水持续时间与土壤有机质质量分数呈正相关。目前存在的问题有：再生水灌溉对土壤和农作物的影响研究不一致,如何消除再生水灌水对地下水和土壤斥水性的影响。认为由于再生水中含有作物正常生长的必要营养元素,若能克服再生水灌溉存在的问题,可缓解淡水资源的压力和减少化肥的使用,避免环境的污染。     

阜阳市农灌区浅层地下水安全开采量评价

针对阜阳市农灌区水文地质条件和浅层地下水运动特点,建立区域浅层地下水多年调节计算模型,通过调节地下水开采量使调节计算末期地下水位埋深能够恢复到起调埋深,达到多年水均衡,得到阜阳市浅层地下水安全开采系数与安全开采量。1956—2010年长系列的计算结果表明,阜阳市多年平均浅层地下水总补给量为17.856亿m3,安全开采系数为0.469,安全开采量为8.374亿m3;结合以农灌区为主的阜阳市用水过程特点,采用等比例法对浅层地下水安全开采量进行年内分配,确定了阜阳市浅层地下水的年内逐月安全开采过程。