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.     

CPSP模型在华北井灌区农业水管理中的应用

为研究不同农业水管理措施对区域水平衡的影响,选择北京市大兴区为华北井灌区代表性研究区,以CPsP模型为技术支持,研究了提高灌溉水利用率、采用亏缺灌溉、改善农业种植结构及利用区外水源等不同水管理措施影响下区域水平衡、区域耗水、区域取水及用水指标的变化规律.结果表明,在资源型缺水区域,提高灌溉水利用率、采用非充分灌溉及改善农业种植结构在一定程度上能缓解区域水资源紧缺的压力,特别是采用非充分灌溉及改善作物种植结构能显著减少区域取水及耗水总量,并能减少地表水及地下水的补给量中回归水所占比例,在缓解区域水资源紧缺压力的同时也降低了区域水质遭受回归水污染风险.另外,在未来情景中,因经济快速发展及人口持续增长,工业及居民生活用水量增加,区域水资源供需矛盾将会加剧,为确保区域水资源良性循环,势必采取积极有效的水资源管理模式.     

基于RS和GIS的灌区增产净效益最大配水模型

在有限供水条件下,为了使全灌区增产净效益达到最大。研究依据非充分灌溉中的调亏灌溉原理和作物的水分生产函数,推导出作物产量与土壤含水率之间的函数关系,并建立了全灌区某次供水增产净效益最大的优化配水模型。根据RS技术能够快速获取信息的特点,以陕西关中冯家山水库北干十一支灌区为例,用RS技术获取灌区土壤含水率情况,再用GIS计算出不同作物灌溉需水量数据,并根据来水量用Matlab计算软件对模型进行求解,可快速获得各斗渠优化配水量。模型在求解时不受灌区类型的限制,因此,模型具有较强的通用性、可操作性和推广性。     

Deficit irrigation in maize for reducing agricultural water use in a Mediterranean environment

Research on crop response to deficit irrigation is important to reduce agricultural water use in areas where water is a limited resource. Two field experiments were conducted on a loam soil in northeast Spain to characterize the response of maize (Zea mays L.) to deficit irrigation under surface irrigation. The growing season was divided into three phases: vegetative, flowering and grain filling. The irrigation treatments consisted of all possible combinations of full irrigation or limited irrigation in the three phases. Limited irrigation was applied by increasing the interval between irrigations. Soil water status, crop growth, above-ground biomass, yield and its components were measured. Results showed that flowering was the most sensitive stage to water deficit, with reductions in biomass, yield and harvest index. Average grain yield of treatments with deficit irrigation around flowering (691 g m⁻²) was significantly lower than that of the well-irrigated treatments (1069 g m⁽²). Yield reduction was mainly due to a lower number of grains per square metre. Deficit irrigation or higher interval between irrigations during the grain filling phase did not significantly affect crop growth and yield. It was possible to maintain relatively high yields in maize if small water deficits caused by increasing the interval between irrigations were limited to periods other than the flowering stage. Irrigation water use efficiency (IWUE) was higher in treatments fully irrigated around flowering.     

Optimisation model for water allocation in deficit irrigation systems: I. Description of the model

In this paper, an economic optimisation model for hydrologic planning in deficit irrigation systems is proposed. Irrigation water allocation between agricultural demands is carried out following an economic efficiency criterion with the aim of maximising the overall economic benefits obtained, allocating available water to each user as a function of the water’s profit margin. Water resources constraints in the system are considered. Aggregated economic functions for each irrigation district are generated optimising the water used for the cropping pattern. Stochastic nature of water availability and irrigation requirements have been taken into account.Due to the complexity of the system, the problem has been broken down into three independent optimisation sub-problems that perform hierarchically. Each of these sub models takes into account a different resolution level of the system: crop, irrigation district and the whole basin.The proposed model has been used in a subsequent paper to optimise water allocation planning in a small basin in southern Spain; the Bembézar system.     

调亏灌溉对日光温室青茄品质和耗水规律的影响

在日光温室滴灌条件下采用小区试验方法,研究了不同生育期不同程度调亏灌溉对青茄耗水规律、产量、品质和水分利用效率的影响。结果表明,温室青茄耗水高峰出现在成熟采摘期,该阶段耗水模系数在49.96%～64.11%之间;苗期的耗水量最小,其阶段耗水模系数在8.64%～16.68%之间。苗期和成熟采摘期适度调亏灌溉(灌水定额为适宜供水的80%)可提高青茄产量和水分利用效率,开花坐果期水分过度亏缺(灌水定额为适宜供水的60%)对青茄品质有所改善,但显著降低青茄产量和灌溉水利用效率。综合考虑产量和品质,拟定日光温室青茄滴灌条件下适宜的灌溉制度为,灌水周期10d,苗期和成熟采摘期适度亏水,灌水定额分别为12mm和20mm;开花坐果期宜充分灌溉,灌水定额为25mm。     

The effect of water supply uncertainty on farmers’ choice of crop portfolio

This paper analyzes the effect of water supply uncertainty on farmers’ choice of crop portfolio. The paper presents an innovative model to estimate the value of uncertainty of water supply, and then tests the model using data from Israel. The modeling results provide support to the hypothesis that uncertainty induces farmers to prefer crops whose growth requires less agricultural capital accumulation, despite their lower profitability (agricultural capital referring to trees and other plants which take a significant period of time to mature). This is due to the risk that in a given year water supply will fall below a certain minimal level, thereby causing loss of all accumulated capital. The paper also examines a government intervention policy for mitigating uncertainty: use of reclaimed wastewater in crop irrigation as a supplement for freshwater supply. The costs associated with constructing the required wastewater reclamation and supply facilities are compared to the benefits of additional farm income earned through a more certain on-farm water supply. It is shown that under certain conditions implementation of this policy is indeed economically worthwhile.     

Effect of different drip irrigation regimes on sugar beet (Beta vulgaris L.) yield, quality and water use efficiency in Middle Anatolian, Turkey

Agricultural production has forced researchers to focus on increasing water use efficiency by improving either new drought-tolerant plant varieties or water management for arid and semi-arid areas under water shortage conditions. A field study was conducted to determine effects of seasonal deficit irrigation on plant root yield, quality and water use efficiency (WUE) of sugar beet for a 2-year period in the semi-arid region. Irrigations were applied when approximately 50–55% of the usable soil moisture was consumed in the effective rooting depth at the full irrigation (FI) treatment. In deficit irrigation treatments, irrigations were applied at the rates of 75, 50 and 25% of full irrigation treatment on the same day. Irrigation water was applied by a drip irrigation system. Increasing water deficits resulted in a relatively lower root and white sugar yields. The linear relationship between evapotranspiration and root yield was obtained. Similarly, WUE was the highest in DI25 irrigation conditions and the lowest in full irrigation conditions. According to the averaged values of 2 years, yield response factor (k _y ) was 0.93 for sugar beet. Sugar beet root quality parameters were influenced by drip irrigation levels in both years. The results revealed that irrigation of sugar beet with drip irrigation method at 75% level (DI25) had significant benefits in terms of saved irrigation water and large WUE, indicating a definitive advantage of deficit irrigation under limited water supply conditions. In an economic viewpoint, 25% saving of irrigation water (DI25) caused 6.1% reduction in the net income.     

Financial analysis of wine grape production using regulated deficit irrigation and partial-root zone drying strategies

Cost-benefit analysis was performed to determine the profitability of producing wine grapes under different irrigation regimes. Vines irrigated by regulated deficit irrigation (RDI) and partial root-zone drying (PRD) were compared with vines grown under full irrigation in a typical vineyard in a semiarid environment with scarce water resources (south-eastern Spain) during three consecutive years. Five irrigation treatments were applied. The Control treatment irrigated at 60% of the ETc (Crop evapotranspiration) throughout the orchard cycle. PRD-1 and RDI-1 provided deficit irrigation from fruit set to harvest (irrigated 30% ETc) and post-harvest (45% ETc). PRD-2 and RDI-2 provided deficit irrigation from fruit set to harvest (irrigated 15% ETc) and post-harvest (45% ETc). From an economic point of view, only the Control, PRD-1 and RDI-1 treatments were economically viable since their profitability indicators were positive, although low, especially PRD-1. The more severe deficit irrigated treatments (PRD-2 and RDI-2) were unviable. The most profitable treatment was the Control which had a Net Margin/total cost ratio (NM/C) (representing the overall profitability of the vineyard) of 25.37% compared with the 1.90% of RDI-1 and 0.57% of PRD-1. The threshold price of water indicates that only the Control remains profitable with higher water prices of up to 0.46 € m⁻³. When the cost-benefit analysis took into account the extra quality achieved in PRD-2 and RDI-2, it indicated that these treatments, which were otherwise economically unviable, achieved high returns (17 and 16%, respectively) and were close to the Control treatment. Thus, a low or moderate bonus that encourages extra berry quality for premium wine production would make deficit irrigation practices profitable. Moreover, the financial indices estimated suggest that in the present situation, and with our soil and climatic conditions, PRD is less economically profitable (higher installation cost, lower NM/C, and threshold price of water) than RDI under the same conditions.     

遗传算法在河西绿洲菘蓝灌溉决策优化中的应用

为缓解河西绿洲菘蓝种植水资源供需矛盾,解决灌溉过程中存在的灌溉决策粗放问题,提高灌溉水利用效率。本文通过参照Jensen模型、水量平衡方程等,根据河西绿洲干旱少雨的环境特征及菘蓝种植过程中各生育期耗水强度不同的生长规律,构建菘蓝灌溉决策模型并利用遗传算法对有限水资源在菘蓝灌溉中的合理分配进行求解。同时综合考虑各生育期灌溉水量约束条件、有效降水量、灌溉成本、产量等因素,在非充分灌溉理论指导下利用遗传算法结合现有菘蓝种植数据对灌溉决策进行优化,以达到节水、高效高产的目的,优化结果显示肉质根轻度水分亏缺可以显著提高灌溉水利用效率,同实际种植灌溉情况相符。     

Land allocation conditioned on El Niño-Southern Oscillation phases in the Pampas of Argentina

The El Niño-Southern Oscillation (ENSO) contributes to the vulnerability of crop production to climate variability in the Pampas region of Argentina. Predictability of regional climate anomalies associated with ENSO may provide opportunities to tailor decisions to expected climate, either to mitigate expected adverse conditions or to take advantage of favorable conditions. Model analysis was used to explore the potential for tailoring land allocation among crops to ENSO phases at the farm scale in two sub-regions of the Pampas. The model identifies as a function of risk preferences and initial wealth the crop mix that maximizes expected utility of wealth at the end of a 1-year decision period based on current costs and prices, and crop yields simulated for each year of historical weather. The model reproduced recent land allocation patterns at the district scale under moderate risk aversion, and predicted increasing diversification with increasing risk aversion. Differences in land allocation among ENSO phases were consistent with known climate response to ENSO, and crop response to water availability. Tailoring land allocation to ENSO phase increased mean net farm income between US$5 and $15 ha⁻¹ year⁻¹ relative to optimizing the crop mixture for all years, depending on location, risk aversion and initial wealth. The relationship between potential value of ENSO information and risk aversion was not monotonic, and differed between locations. Crop mix and information value also varied with crop prices and initial soil moisture. There are potential financial benefits of applying this approach to tailoring decisions to ENSO phases.     

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.     

Impact of sustained deficit irrigation on spearmint (<Emphasis Type="Italic">Mentha spicata</Emphasis> L.) biomass production,oil yield,and oil quality

Crop response to deficit irrigation is an important consideration for establishing irrigation management strategies when water supplies are limited. This study evaluated the response of native spearmint to water deficits applied using overhead sprinklers in eastern Washington, US. Five levels of irrigation were applied ranging from full irrigation (100%) to 5% of weekly averaged full crop water needs. Soil water monitoring with soil water balance was used to estimate soil water deficits for irrigation scheduling and soil water use. Mint oil yields, oil components, dry matter production, and the water-use efficiency of the spearmint were assessed. There was significant reduction in fresh mint hay (harvested biomass) yield with increasing water deficit. However, spearmint oil yields remained generally uniform across irrigation treatments at the first cutting but decreased at the driest plots during the second harvest due to a loss of plant stand. The wet harvest index and water-use efficiency improved significantly for both harvests with increasing water deficit. Hay yield, oil yield, wet harvest index, and water-use efficiency are pooled across sides and replicate blocks to provide trends with changes in maximum evapotranspiration. The three major monoterpenes show changes suggesting less mature oil yields. The study demonstrates the feasibility of sustaining native spearmint yields under managed deficit irrigations for deficits not lower than 0.5 ETc.     

Increasing water productivity in crop production—A synthesis

Scarcity of water resources and growing competition for water in many sectors reduce its availability for irrigation. Effective management of water for crop production in water scarce areas requires efficient approaches. Increasing crop water productivity (WP) and drought tolerance by genetic improvement and physiological regulation may be the means to achieve efficient and effective use of water. But only high water productivity values carry little or no interest if they are not associated with high or acceptable yields. Such association of high (or moderate) productivity values with high (or moderate) yields has important implications on the effective use of water. In this paper we discussed the factors affecting water productivity, and the possible techniques to improve water productivity. A single approach would not be able to tackle the forthcoming challenge of producing more food and fiber with limited or even reduced available water. Combining biological water-saving measures with engineering solutions (water saving irrigation method, deficit irrigation, proper deficit sequencing, modernization of irrigation system, etc.), and agronomic and soil manipulation (seed priming, seedling age manipulation, direct- or wet-seeded rice, proper crop choice, integrating agriculture and aquaculture, increasing soil fertility, addition of organic matter, tillage and soil mulching, etc.) may solve the problem to a certain extent. New scientific information is needed to improve the economic gains of WP because the future improvements in WP seem to be limited by economic rather than a lack of technological means.     

Financial feasibility of implementing regulated and sustained deficit irrigation in almond orchards

This study aims to assess the long-term economic viability of deficit irrigation (DI) strategies in almond trees (cv. Marta) grown in a semiarid area (southeast Spain). A discounted cash flow analysis (DCFA) was performed to determine the profitability of the different irrigation regimes. Four irrigation treatments were evaluated over the first 6 years of an almond plantation: (1) full irrigation (FI); (2) regulated deficit irrigation (RDI) receiving 40 % ETc during kernel-filling and 100 % ETc during the remainder of the growing season; (3) mild-to-moderate sustained deficit irrigation (SDI_mm), irrigated at 75 % ETc (first half of the experiment) and 60 % ETc (second half of the experiment) over the entire growing season; and (4) moderate-to-severe SDI (SDI_ms), irrigated at 60 % ETc (first half of the experiment) and 30 % ETc (second half of the experiment) over the whole growing season. Irrigation water profit was mainly determined by the annual volume of irrigation water applied (water costs are around 50 % of variable costs). DCFA indicates that RDI and SDI_mm are the most economically feasible treatments, whereas FI and SDI_ms presented a similar degree of profitability over the 6-year period. Simulation outputs derived for the whole useful life of the investment indicate that SDI_mm would be the most suitable irrigation treatment to be adopted by almond farmers in the study area. We conclude that in a context of water scarcity, DI is a financially feasible alternative to FI.     

Effect of water shortage on yield, and protein and mineral compositions of drip-irrigated sweet corn in sustainable agricultural systems

Water is a natural resource of prime value that is very often limited and costly, particularly in semi-arid regions. While traditional irrigation methods increase the amount of surface runoff, drip irrigation provides efficient use of the limited water resources. This study was conducted to determine the water-yield relationship and the quality of sweet corn grown under deficit drip irrigation in 1998 and 1999 in Sanliurfa, Turkey. Irrigation treatments analysed in this study were full irrigation as well as 10, 20 and 30% deficiency of Class A pan evaporation. In both years, water use efficiency ranged between 1.18 and 1.36 kg m⁻³, and irrigation water use efficiency ranged between 1.36 and 1.62 kg m⁻³. The yield response factor (k_y) or the ratio of the decrease in relative yield to the decrease in relative water consumption varied from 0.82 to 1.43, and the water-saving rate ranged from 10.9 to 31.1%. The relationships between fresh ear yield and the irrigation treatments were statistically significant (P < 0.01), and the yield decreased with increasing deficit irrigation. Root dry matter increased with water shortage. Maximum values of leaf area index were obtained at full irrigation, whereas the lowest values were found at 30% water deficiency. The values of the deficit irrigation stress index increased with decreasing water application. Although the protein content increased, the Fe, Zn and Cu concentration of the kernels decreased with increasing water deficiency. Despite the reduction of fresh ear yield with deficit irrigation, the number of marketable ears at 10% water deficiency was still high and acceptable for sweet corn (var. Reward) in south-eastern Turkey.     

Deficit irrigation under water stress and salinity conditions: The MOPECO-Salt Model

In both arid and semi-arid areas the use of saline water for irrigation is a common practice, even though it may cause a drop in crop yield and progressive soil salinization. In order to determine the most suitable irrigation strategy for higher yield, profitability, and soil salinity management of certain crops, the MOPECO-Salt Model has been developed. This model was first validated in the Eastern Mancha Agricultural System in Albacete (Spain) through a test carried out on onion crop in April-September 2009, where the simulated yield was 2% lower than the observed one. The model was then tested at Tal Amara Research Station in the Central Bekaa Valley Agricultural System (Lebanon) using data from a 5-year experiment on the effects of deficit irrigation on two cultivars of potato (Spunta: July-October 2001, and June-September 2002; and Agria: March-August 2004, 2005, and 2007). Furthermore, these results were compared with those obtained through AquaCrop, which does not currently assess crop response to salinity. Differences between observed and simulated yields were lower than 3% for MOPECO-Salt and up to 12% for AquaCrop. According to findings from simulations, the irrigation strategies without leaching fraction employed in both areas are remediable since the off-season rainfall is sufficient to wash out soluble salts supplied with irrigation water. Results showed that as much as 14.4% water could be saved when this strategy was adopted for onion crops.     

调亏灌溉技术及对葡萄果实品质的影响

由于全球变暖,水资源短缺的风险越来越大,为此优化传统栽培模式,实行节水灌溉势在必行,调亏灌溉是提高水分利用效率的关键技术。本文首先深入探讨了调亏灌溉的机理,从葡萄树体的生长状况、根系的发育情况以及相关蛋白的表达调控等多个角度进行了综合分析。其次文章对分期调亏灌溉、根系分区灌溉和隔行交替灌溉这三种具体的调亏灌溉模式进行了详细的概述。文章进一步探讨了不同灌溉时期对葡萄生长发育的影响,以及不同物候期对水分的需求及如何根据葡萄的生长周期来合理安排灌溉时间。最后,文章总结了调亏灌溉对葡萄果实中糖分、酸度、酚类化合物以及香气物质等关键品质因素的影响。通过对调亏灌溉机理的深入研究,以及对不同灌溉模式和时期影响的探讨,为科学管理葡萄园,实现节水增效,促进农业可持续发展奠定理论基础。     

Irrigation scheduling strategies for cotton to cope with water scarcity in the Fergana Valley, Central Asia

The Central Asian countries face high water scarcity due to aridity and desertification but excess water is often applied to the main irrigated crops. This over-irrigation contributes to aggravate water scarcity problems. Improved water saving irrigation is therefore required, mainly through appropriate irrigation scheduling. To provide for it, after being previously calibrated and validated for cotton in the Fergana region, the irrigation scheduling simulation model ISAREG was explored to simulate improved irrigation scheduling alternatives. Results show that using the present irrigation scheduling a large part of the applied water, averaging 20%, percolates out of the root zone. Several irrigation strategies were analyzed, including full irrigation and various levels of deficit irrigation. The analysis focused a three-year period when experiments for calibration and validation of the model were carried out, and a longer period of 33 years that provided for an analysis considering the probabilities of the demand for irrigation water. The first concerned a wet period while the second includes a variety of climatic demand conditions that provided for analyzing alternative schedules for average, high and very high climatic demand. Results have shown the importance of the groundwater contribution, mainly when deficit irrigation is applied. Analyzing several deficit irrigation strategies through the respective potential water saving, relative yield losses, water productivity and economic water productivity, it could be concluded that relative mild deficits may be adopted. Contrarily, the adoption of high water deficit that produce high water savings would lead to yield losses that may be economically not acceptable.     

膜下调亏滴灌对制种玉米耗水规律及产量的影响

通过大田膜下调亏滴灌试验,测定了制种玉米叶面积指数、耗水量和产量等指标。结果表明,拔节—抽穗期缺水抑制了叶面积的生长,对产量负面影响极为显著,水分利用效率显著降低;灌浆—成熟期缺水对叶面积指数和产量影响甚微,而水分生产效率却显著提高,通过建立产量与叶面积指数以及叶面积指数与日耗水强度模型,提出了在抽穗期充分供水,苗期和成熟期减小供水、保持适度的水分亏缺的制种玉米节水高产水分调控模式。