农业节水措施对地下水涵养的作用及其敏感性分析

以北京市大兴区为研究区,利用经校验的水平衡模型,通过调整灌溉满足率和灌溉水利用系数,探讨了不同农业节水措施对增加地下水补给量和减少地下水开采量的作用及其敏感性。结果表明,不同水文年型下,降低灌溉满足率及提高灌溉水利用系数都能减少地下水开采量,且降低灌溉满足率对减少地下净开采量的作用更为显著,有利于区域地下水涵养。在参数取值范围内,地下水净开采量对灌溉满足率的敏感性较大,而地下水补给量对灌溉水利用系数的敏感性较高。与提高灌溉水利用系数相比,对资源性缺水区域,采用先进节水技术,适度降低区域灌溉满足率,对促进水资源持续有效利用及加大地下水涵养具有更显著的效果。     

Farm-level perspectives regarding irrigation water prices in the Tulkarm district, Palestine

Agriculture consumes about 70% of water available in the Occupied Palestinian Territories. Domestic and industrial users utilize 30% of the water supply. Water resource managers are considering the policy of reallocating a portion of the water supply from agriculture to other uses. It is believed that increasing irrigation water prices could influence water consumption and thus make water available for non-agricultural (more economic) uses. This paper examines the impacts of water pricing on agricultural water consumption and farming profitability and provides some guidelines for policy makers regarding water pricing as a tool to manage scarce water resources. We estimate a regression model describing agricultural water consumption as a function of water prices, irrigated land area, farm income, and irrigation frequency, using data collected in a survey of about 150 farmers in the Tulkarm district. We conclude that irrigation water prices are perceived as high and comprise a large portion of total farming expenses. Therefore, attempts to increase irrigation water prices in the Tulkarm district might jeopardize farming feasibility and might have substantial impacts on agricultural water consumption. Nevertheless, many farmers would continue farming even if the water prices were increased beyond their willingness to pay threshold.     

玛纳斯河灌区农户农业灌溉水价承受能力研究

从玛纳斯河灌区农户种植棉花平均生产成本和收入情况、水费占成本、收入的比例情况、农户可接受的灌溉水费占单位面积投入比例、农户对现行灌溉水价的评价及对水价构成的认识等方面进行了抽样调查.在此基础上对灌区农户灌溉水价的承受能力进行了分析,给出了该灌区农户水费承受能力指标及2006年该灌区农户可承受的平均终端灌溉水价为0.110 9元/m 3 .为该灌区制定农业灌溉水价改革政策、提高农业水资源利用效率等提供基础资料.     

Economic impacts on farm households due to water reallocation in China's Chaobai watershed

Our study area in the Chaobai watershed, upstream of Miyun Reservoir, has been undergoing agricultural water transfers to downstream municipal uses in Beijing. We examine the impacts of water reallocation on crop production and farmers’ income and discuss issues relating to current compensation mechanisms. We use data from a survey of 349 farm households and their farm plots in the upper Chaobai watershed within Hebei province. Water reallocation from upstream to downstream areas has reduced agricultural water supply and the area irrigated. Regression results show that in plots deprived of irrigation, maize yields decrease by 21% and crop revenues decline by 32%. On average, losing irrigation on one hectare of cultivated land reduces net crop income by 2422 yuan. We examine compensation arrangements and social equity for the major policies implemented in the region and we identify gaps between current compensation levels and farmers’ income and production losses. The current compensation received by farmers is generally lower than the losses incurred due to reduced irrigation. A more appropriate compensation mechanism is called for in future water transfers.     

Irrigation water prices for farmer-managed irrigation systems in Tanzania: a case study of Lower Moshi irrigation scheme

A computer program model for pricing irrigation water among beneficiaries was developed and tested. The data used for the purpose was collected from Lower Moshi farmer-managed irrigation scheme (FMIS) in northern part of Tanzania as a case study. The scheme has two intakes; namely Rau and Mabogini irrigation systems. Allam's mathematical model for allocating irrigation water price which was developed in Egypt (Allam, 1987) was adopted and adapted for the purpose. The results indicate that the irrigation water price depends on a number of structures serving the area, their installation costs, amount of water received by each tertiary block and water rights. The prices differ between different tertiary blocks within the same system and also between two systems that exist in Lower Moshi Irrigation Scheme (LMIS). This indicates that the model can be used as a tool by designers and planners for selecting the best designed irrigation system that farmers can afford to pay for its operation, maintenance and management. The mean irrigation water price value for Mabogini is Tshs. 12 151/-¹ while that of the Rau system is 10 414/-. To maintain uniformity of irrigation water price in the scheme, it is recommended that a mean value of Tshs. 11 283/- is used. Generally, farmers in Tanzania are used to contribute one bag of paddy which costs about Tshs. 10 000/- for maintenance works. Therefore, the irrigation water price derived from the model is reasonable and one the farmers can afford.     

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.     

Using economic incentives and regulations to reduce seawater intrusion in the Batinah coastal area of Oman

Excessive groundwater abstraction is a major problem in Oman, primarily in the Batinah coastal area where it results in seawater intrusion. The Government began to address the problem in the 1990s by encouraging the use of more efficient irrigation systems, replacing date palms with winter vegetable crops and using treated wastewater for municipal irrigation. However, 15 years later, seawater intrusion in the Batinah aquifers is still advancing at an alarming pace. This paper analyses the relative merits of strategies to control groundwater pumping based on water quotas, electricity quotas and electricity pricing. A cost benefit approach is used to evaluate the feasibility of three strategies over a period of 25 years and to compare them to the “business as usual” option. Results show that the net present loss to the community when no active policy is implemented amounts to (−$288) million. Imposing water quotas on tubewells would give a net present benefit of $153 million. However, such quotas would give the lowest present benefit and create inequity among farmers. Other possible approaches would be to control the pumping of groundwater from all wells - tubewells and dug wells - by enforcing energy quotas and by increasing the price of electricity used to pump water. The net present benefits would be greater and the costs to farmers would be more fairly spread. The results of cost-benefit analysis show that enforcing an electricity quota, coupled with removal of the subsidy on the electricity price, is the easiest and most equitable solution to implement.     

农业水价改革情景中农户的节水意愿——基于河北省地下水超采区的实地调研

农业水价改革是黄淮海平原地下水压采的重要措施之一。基于河北省地下水超采综合治理区的实地调研,运用交叉分析法和二元Logistic模型分析了农业水价改革情景中农户节水意愿的影响因素。调查结果显示75.32%的农户在农业水价改革情景中没有节水意愿。研究结果表明年龄越大、家中有耕地参加休养生息政策的农户,在农业水价改革情景中的节水意愿越强;农户认为冬小麦春灌节水会导致小麦减产的程度越高,节水意愿越弱。因此得出推广农作物抗旱育种技术以及促进田间灌溉技术升级、加强农业节水宣传和培训、设计并实施系统和综合的农业水价改革三点政策含义。     

Water productivity in smallholder irrigation schemes in South Africa

This study investigates the productivity and value of water in two smallholder irrigation schemes (Zanyokwe and Thabina) in South Africa. We apply the residual valuation method (RVM), willingness to pay (WTP) and cost-based approaches (CBA) (i.e. accounting costs of operation and maintenance) to evaluate water productivity and values per crop, per farm, and by scheme. In both schemes, water value estimated by the RVM for vegetables (cabbage, tomatoes and butternuts) is greater than water value for dry maize. At the farm and scheme levels, a comparison was made between gross margin per m³ of water, WTP per m³ and accounting cost per m³ to estimate the relative value of water productivity. The active farmers in the Zanyokwe scheme have lower WTP per m³ (R0.03) than the gross margin of output (R0.69). Also, the accounting cost (R0.084) per m³ of water is less than the gross margin. In the Thabina scheme, active farmers are willing to pay (R0.19) per m³ of water. Hence farmers in Thabina are ready to pay as much as three times the proposed costs of O&M (R0.062) per m³ of water used. Both the accounting cost and willingness to pay are less than the gross margin per m³ of water in the Zanyokwe scheme. Our findings indicate that extension and training may be required to improve the productive use of water for those farmers whose returns are insufficient to cover the cost of supply.     

关于农村安全饮用水水价的思考

合理的水价应包括3个组成部分:资源水价、工程水价和环境水价。结合我国农村的实际情况,给出农村安全饮用水水价的制定方法。该水价应以成本水价加微利来确定,同时还应考虑农民的支付意愿和承受能力,并且根据经济情况按地区分类指导。     

Impact of different water price levels on irrigated agriculture in Northern Jordan Valley

A linear programming model was developed to assess the impact of different water prices on cultivated areas, irrigation water demand, net income and optimal cropping pattern in the Northern Jordan Valley (NJV). The results reveal that the price for irrigation water does not reflect any elasticity in the range of water prices between 0.01 and 0.06 JD/M³ indicating constant real economic water price of 0.06 JD/M³. The change in cultivated areas as well as water demand (reduction) starts at water price 0.07 JD/M³. The expected reductions under optimal cropping patterns are 5%, 24%, and 60% for cultivated area and 4.7%, 18.9%, and 31% for water demand with water prices at 0.07, 0.1, and 0.16 JD/M³, respectively. Significant reductions in net incomes are resulted with increasing water prices over current average water price of 0.025 JD/M³. The expected reductions in net incomes are 33.6%, 53.8%, and 81.4% at water prices 0.07, 0.1, and 0.16 JD/M³, respectively. This result reflects the low land profitability as a result of low land productivity and/or low farm gate sale prices for most crops grown in NJV. The study also shows the inconsistency in quantity of water supplied and water demanded, leading to unbalanced water budget on monthly level and inconsequence, a noticeable waste in the quantity of available water during winter months, although there is a net surplus of water over the year. While the findings of this research reveal that a water price in the range of 0.07?C0.1 JD/M³ does not significantly influence the farmers' socio-economic parameters in the NJV, it may help reach the stated goal of saving water especially when monthly distributions of irrigation water are based on real crops water demands and actual cropping patterns.     

Access to groundwater and agricultural production in China

Although the ways in which farmers access irrigation services in areas that rely on groundwater have changed over the past decade, little empirical work has measured the impact of these changes. This is surprising given the potential effects—both positive and negative. In this paper we explore the impacts of the emergence of the markets for irrigation services from groundwater on agricultural production - including crop water use and crop yields - and farmer income in northern China. From a survey of 35 randomly sampled villages and 338 households in two provinces (Hebei and Henan Provinces) in 2001 and 2004, we show that when farmers access water from markets for irrigation services, they significantly reduce water use, compared with farmers who have their own tubewells. However, there is no significant difference between the volume of water used by farmers who access irrigation services provided by the village, and the volume used by farmers who access water from markets for irrigation services. Importantly, although water use decreases, we find little effect on either agricultural productivity (yields) or income.     

井渠结合灌区地下水开采方案设计研究——以泾慧渠灌区试验区为例

首先根据泾惠渠灌区试验区近60a的气象、土壤资料,利用CROPWAT模型计算区域冬小麦、玉米、棉花的灌溉需水量。根据研究区需水、供水之间的关系以及渠井适宜比理论提出3种地下水开采方案。在试验区水文地质条件的基础上,运用Visual Modflow软件建立了地下水流数值模型,并从地下水合理埋深、丰枯季地下水量构成等角度,对不同开采方案下的地下水动态变化进行了分析和验证。结果表明:通过对未来年地下水位的预测可知,3种开采方案下的地下水埋深都在合理的埋深范围内;对比分析发现第2种方案的地下水开采所引起的降深适中,开采量有可靠的补给保证,并在丰枯两季形成动态调整,为最优方案。该研究为今后试验区地下水的合理开采提供了科学依据。     

农田灌溉用水权有偿转让机制与农民受益研究

在对我国用水结构变化分析的基础上,对农田灌溉用水转移的潜力进行了调查分析。选择典型灌区,对农田灌溉用水权转让的基本原则、农业初始水权的界定、水权初始分配的程序、农业用水权的有偿转让条件、农业用水权的转让主体、转让的内容、农业用水转移的供水价格与供水年限等进行了研究。分析了政策环境对灌溉用水权有偿转让的影响,提出了依法保护灌溉用水权有偿转让过程中灌区管理部门和农民合法权益的具体措施。     

Estimating the potential gains from water markets: a case study from Tunisia

Water markets can improve water use efficiency through the transfer of water to users who can obtain the highest marginal return from using it. Existing water markets are implemented among farmers or between farmers and urban water companies or hydropower companies. Several studies have shown that farmers may benefit from trading water mainly in countries where water scarcity is increasing and new water supply projects are either very costly or not possible because of environmental concerns. This paper estimates the potential benefits and losses of implementing water market among farmers and between farmers and urban water company in Tunisia. We used linear programming to examine four separate farm models and an aggregate model. The method is applied to an irrigation area of 4500 ha in Northern Tunisia. Results indicate that water trading among farmers would be quite limited and would have a minor impact on farmers’ income. In contrast, the market among farmers and the urban water company offers higher volumes of water trades to urban users and helps increase farmers’ profitability by up to 7.9%. The sale of water to the urban company is accompanied by a decrease in occasional labor by as much as 34.8% and a decrease of up to 17.6% in farmers’ expenditures for inputs and machinery. Additionally, results obtained in this paper show that inter-year storage of irrigation water may be more advantageous than selling water to the urban utility. Whether farmers would opt to sell water or inter-temporarily store it would depend on the establishment of water rights and the empowerment of farmers.     

模糊数学在农业水价中的应用

基于模糊数学理论,综合考虑影响农业水价的环境、经济和社会3方面因素,选取水质、水资源量、人均可支配收入、技术成本投资和农民满意程度5项影响因素,建立了农业水价模糊数学综合评价模型,并应用于实际工程。以云南某大型灌区为例,测算的农业水价为0.99元/m3,与现行水价0.08元/m3差距较大,故应在农民可接受的范围内提高农业水价。合理的农业水价,可减少农业水资源浪费,提高水资源利用率,对实现农业节水具有重要意义。      

宁夏引黄灌区农业水价改革现状分析及思考

近年来,按照国家水利部和宁夏回族自治区建设节水型社会的要求,宁夏引黄灌区全面推行了农业水价改革,取得了一定成效。结合灌区实际情况,详细介绍了灌区水价改革、灌区供水成本及管理处收益现状,分析水价改革中存在的主要问题,并提出建立分灌区、分作物的阶梯水价标准及完善相关配套政策、组织管理、基础建设的具体建议,旨在为宁夏引黄灌区进一步落实水价改革提供参考依据。     

农民对农业水价承受能力研究

农民是农业水价承受的主体，其承受能力的大小决定着农业水价改革的力度和进程，通过对人民胜利渠道灌区农民对农业水价承受能力的调查:揭示了灌区的运行能力是随着农业水价的上调逐步增加的，而用水是逐步减少的;农民对农业水价改革的承受能力是非常有限的;当农业水费占到农民年收入的4%一6%(支出的6%一8%)、农业投入的10%-12%和产出的8%-10%时，农民普遍认为水价合理或者基本合理，表示可以接受、愿意缴纳，说明水费没有超出农民的经济和心理承受能力;提出了促进农业水价改革的综合对策。     

‘More crop per drop’: how to make it acceptable for farmers?

In countries facing water scarcity, governmental water agencies try to transfer this constraint to farmers, e.g. by encouraging them to shift from traditional to localized irrigation methods to save water. However, water shortage is often much less a problem for farmers than soil limitations, their objective being mostly to maximize their income per cultivated area (US$ per hectare rather than per cubic meter of water). This discrepancy can only be solved if governments find ways to ‘transfer’ water scarcity, e.g. through economic incentives such as water pricing and/or subsidies. The aim of this study was to address the question of how to match the interest of both water managers and farmers. We aimed particularly at evaluating whether shifting to drip irrigation is a relevant way to save water and increase farmer's income.Our analysis was based on the interactive impacts among economic, environmental, technical and methodological parameters on the net productivity of two crops. We focused on the case study of Turkey considering two crops with contrasted gross productivity, tomato and cotton, characterized by partial vegetation cover during a large part of crop cycle. A 3D crop energy balance model was applied showing that crop transpiration is increased by up to 10% when shifting from furrow to drip irrigation. These results were used to correct the maximal evapotranspiration (ET_m), estimated with the simple “crop coefficient” (K_c) method, and then used to enhance net productivity estimation both for furrow and drip irrigation.The results suggest that water managers and farmers share a common interest in adopting drip irrigation of tomato. Inversely, interests divergence may increase with low/medium value crops as cotton; the combination between water pricing and subsidies could be a way of agreement, but it would require subsidies for irrigation equipment of at least 40%, for low water tariffs, to 60%, for high water tariffs, to make the transfer from furrow to drip irrigation acceptable. This approach appeared generic enough to be applied for other economic, technical or environmental conditions, to modernize irrigation by harmonizing constraints faced by water managers and farmers.     

Combining hydrological modeling and GIS approaches to determine the spatial distribution of groundwater recharge in an arid irrigation scheme

Accurate quantification of the rate of groundwater (GW) recharge, a pre-requisite for the sustainable management of GW resources, needs to capture complex processes, such as the upward flow of water under shallow GW conditions, which are often disregarded when estimating recharge at a larger scale. This paper provides (1) a method to determine GW recharge at the field level, (2) a consequent procedure for up-scaling these findings from field to irrigation scheme level and (3) an assessment of the impacts of improved irrigation efficiency on the rate of GW recharge. The study is based on field data from the 2007 growing season in a Water Users Association (WUA Shomakhulum) in Khorezm district of Uzbekistan, Central Asia, an arid region that is characterized by a predominance of cotton, wheat and rice under irrigation. Previous qualitative studies in the region reported irrigation water supplies far above the crop water requirements, which cause GW recharge. A field water balance model was adapted to the local irrigation scheme; recharge was considered to be a fraction of the irrigation water losses, determined as the difference between net and gross irrigation requirements. Capillary rise contribution from shallow GW levels was determined with the HYDRUS-1D model. Six hydrological response units (HRUs) were created based on GW levels and soil texture using GIS and remote sensing techniques. Recharge calculated at the field level was up-scaled first to these HRUs and then to the whole WUA. To quantify the impact of improved irrigation efficiency on recharge rates, four improved irrigation efficiency scenarios were developed. The area under cotton had the second highest recharge (895 mm) in the peak irrigation period, after rice with 2,514 mm. But with a low area share of rice in the WUA of <1 %, rice impacted the total recharge only marginally. Due to the higher recharge rates of cotton, which is grown on about 40 % of the cropped area, HRUs with a higher share of cotton showed higher recharge (9.6 mm day^?1 during August) than those with a lower share of cotton (4.4 mm day^?1). The high recharge rates in the cotton fields were caused by its water requirements and the special treatment given to this crop by water management planners due to its strategic importance in the country. The scenario simulations showed that seasonal recharge under improved irrigation efficiency could potentially be reduced from 4 mm day^?1 (business-as-usual scenario) to 1.4 mm day^?1 (scenario with maximum achievable efficiency). The combination of field-level modeling/monitoring and GIS approaches improved recharge estimates because spatial variability was accounted for, which can assist water managers to assess the impact of improved irrigation efficiencies on groundwater recharge. This impact assessment enables managers to identify options for a recharge policy, which is an important component of integrated management of surface and groundwater resources.