Impacts of considering climate variability on investment decisions in Ethiopia

Extreme interannual variability of precipitation within Ethiopia is not uncommon, inducing droughts or floods and often creating serious repercussions on agricultural and nonagricultural commodities. A dynamic climate module is integrated into an economy‐wide model containing a detailed zonal level agricultural structure. This coupled climate‐economic model is used to evaluate the effects of climate variability on prospective irrigation and infrastructure investment strategies, and the ensuing country‐wide economy. The linkages between the dynamic climate module and the economic model are created by the introduction of a climate‐yield factor (CYF), defined at the crop level and varied across Ethiopian zones. Nine sets of variable climate (VC) data are processed by the coupled model, generating stochastic wet and dry shocks, producing an ensemble of potential economic prediction indicators. Analysis of gross domestic product and poverty rate reveal a significant overestimation of the country's future welfare under all investment strategies when climate variability is ignored. The coupled model ensemble is further utilized for risk assessment to guide Ethiopian policy and planning.     

Global food demand,productivity growth,and the scarcity of land and water resources: a spatially explicit mathematical programming approach

In the coming decades, an increasing competition for global land and water resources can be expected, due to rising demand for food and bio‐energy production, biodiversity conservation, and changing production conditions due to climate change. The potential of technological change in agriculture to adapt to these trends is subject to considerable uncertainty. In order to simulate these combined effects in a spatially explicit way, we present a model of agricultural production and its impact on the environment (MAgPIE). MAgPIE is a mathematical programming model covering the most important agricultural crop and livestock production types in 10 economic regions worldwide at a spatial resolution of three by three degrees, i.e., approximately 300 by 300 km at the equator. It takes regional economic conditions as well as spatially explicit data on potential crop yields and land and water constraints into account and derives specific land‐use patterns for each grid cell. Shadow prices for binding constraints can be used to valuate resources for which in many places no markets exist, especially irrigation water. In this article, we describe the model structure and validation. We apply the model to possible future scenarios up to 2055 and derive required rates of technological change (i.e., yield increase) in agricultural production in order to meet future food demand.     

绿水资源研究进展及评述

[目的]基于蓝水绿水概念,综述总结国内外绿水资源的研究进展和发展趋势,以期为国内绿水模拟和绿水管理研究提供相关参考依据。[方法]通过文献分析法和比较归纳法,阐述了绿水资源在水资源评估规划中的重要作用和开发利用潜力,评价了国内外绿水模拟的研究方法、研究进展与局限性因素,分析了气候变化和人类活动对绿水资源的影响,探讨了流域绿水管理的基本理念与应用发展。[结果](1)绿水资源表示水循环通过降水渗透入土壤非饱和层并由植物蒸腾或土壤蒸发返回大气层的水汽,是农业作物生产的重要基础,但是通常被传统流域水资源管理所忽视。(2)绿水模拟分析结果表明,全球尺度的陆地水资源总量中绿水资源平均占65%,全球尺度农业用地(作物生产期)的绿水资源比例平均占82%,因此绿水的开发利用潜力相对较大,忽视绿水资源量可能会低估水资源可用性。(3)绿水参数率定、遥感ET数据校准、时空尺度转换和不确定性分析等关键问题是提升绿水模拟精度的重点研究方向。(4)基于气候变化和人类活动影响下,水资源稳定性相对减弱的可能趋势,将绿水纳入流域水资源管理体系,有利于客观评估水资源量,能够为应对解决水缺乏、水波动与水冲突等水资源问题拓宽思路。(5)绿水管理是合理优化配置流域蓝水绿水资源,协调平衡流域整体社会经济与生态环境效益,且兼顾上下游公平效率的新型流域水资源开发管理模式。[结论]应对水资源问题的两个基本方向即“开源节流”,绿水资源作为开源的重要方向,绿水管理作为节流的基本措施,理应受到重点关注。绿水概念和绿水管理是在水量平衡基础上,实现流域水资源合理优化配置及高效利用的可行途径。     

干旱区塔里木河流域地下水资源统筹管理研究

地下水资源是流域水资源的重要组成部分,是干旱区生态环境的命脉。塔里木河流域地下水资源具有典型的"公共池塘资源悲剧"特征,存在地表水与地下水管理分割、统筹协调不足等问题。流域地下水资源开发利用处于相对失控状态,地下水资源的过度开发利用,造成部分地区河道断流、湖泊水位下降,产生了一系列生态环境问题。根据存在的问题,文章分别从完善流域与区域的地下水资源管理法规体系,完善源流与干流地下水资源管理体制,建立地下水库与地表水统筹调度模式,建立流域地下水与地表水资源统筹管理模式等方面提出了管理对策,以期促进塔里木河流域可持续发展。     

Evaluation of drought management in irrigated areas

This paper focuses on the economic consequences of droughts for the irrigation sector. We develop a dynamic‐recursive mathematical programming farm model that assumes imperfect mobility of capital and labour as well as rational expectations about future water availability. The model is calibrated to 12 representative farms belonging to three irrigation communities of the Guadalquivir Basin (south Spain) and used to simulate the 1991–1997 period, which included 3 years of intense drought. Results indicate that the drought imposed significant costs on farmers, but show also that water managers partly exacerbated these costs by allocating excessive amounts of water to irrigators in the abundant years. The model is also used to evaluate the benefits of a perfect water supply forecast and to simulate the economic gains of a voluntary water banking scheme. Results show that the benefits resulting from the perfect forecast of water supply 1 year ahead would represent a relative gain of 5%. However, a voluntary banking system would allow farmers to increase their benefits by 32–82% depending on the supply system.     

Macro–micro feedback links of water management in South Africa: CGE analyses of selected policy regimes

The pressure on an already stressed water situation in South Africa is predicted to increase significantly under climate change, plans for large industrial expansion, ongoing rapid urbanization, and government programs to provide access to water to millions of previously excluded populations. This article employs a general equilibrium approach to examine the economy‐wide impacts of selected macro and water‐related policy reforms on water use and allocation, rural livelihoods, and economy at large. The analyses reveal that implicit crop‐level water quotas reduce the amount of irrigated land allocated to higher‐value horticultural crops and create higher shadow rents for production of lower‐value water‐intensive field crops, such as sugarcane and fodder. Accordingly, liberalizing local water allocation within irrigation agriculture is found to work in favor of higher‐value crops, and expand agricultural production and exports and farm employment. Allowing for water trade between irrigation and nonagricultural uses fuelled by higher competition for water from urbanization leads to greater water shadow prices for irrigation water with reduced income and employment benefits to rural households and higher gains for nonagricultural households. The analyses show difficult trade‐offs between general economic gains and higher water prices, which place serious questions on subsidizing water supply to irrigated agriculture, i.e., making irrigation subsidies much harder to justify.     

Valuing groundwater recharge through agricultural production in the Hadejia-Nguru wetlands in northern Nigeria

This study applies a production function approach to value the groundwater recharge function of the Hadejia‐Nguru wetlands in northern Nigeria. The groundwater recharge function supports dry season agricultural production which is dependent on groundwater abstraction for irrigation. Using survey data this paper first carries out an economic valuation of agricultural production, per hectare of irrigated land. We then value the recharge function as an environmental input into the dry season agricultural production and derive appropriate welfare change measures. Welfare change is calculated using the estimated production functions and hypothetical changes in groundwater recharge and hence, groundwater levels. By focusing on agricultural production dependent solely on groundwater resources from the shallow aquifer, this study establishes that the groundwater recharge function of the wetlands is of significant importance for the floodplain.     

Impacts of climate change on lower Murray irrigation*

This article evaluates irrigated agriculture sector response and resultant economic impacts of climate change for a part of the Murray Darling Basin in Australia. A water balance model is used to predict reduced basin inflows for mild, moderate and severe climate change scenarios involving 1, 2 and 4°C warming, and predict 13, 38 and 63% reduced inflows. Impact on irrigated agricultural production and profitability are estimated with a mathematical programming model using a two‐stage approach that simultaneously estimates short and long‐run adjustments. The model accounts for a range of adaptive responses including: deficit irrigation, temporarily following of some areas, permanently reducing the irrigated area and changing the mix of crops. The results suggest that relatively low cost adaptation strategies are available for a moderate reduction in water availability and thus costs of such a reduction are likely to be relatively small. In more severe climate change scenarios greater costs are estimated. Adaptations predicted include a reduction in total area irrigated and investments in efficient irrigation. A shift away from perennial to annual crops is also predicted as the latter can be managed more profitably when water allocations in some years are very low.     

干旱区流域地下水生态调节与监测预警研究

[目的]干旱区流域地下水资源与生态环境具有紧密的响应关系。塔里木河流域是我国典型的干旱荒漠区,研究地下水对生态的调节功能以及对地下水的监测预警,对干旱区流域可持续发展具有重要的作用。[方法]根据流域地下水自动监测系统的长期监测,研究选取塔里木河上游阿拉尔、新渠满,中游英巴扎,下游恰拉、阿拉干共5个断面31眼监测井进行地下水位检测。[结果]监测显示,塔里木河流域上、中游的地下水位良好,下游地下水位较低,生态环境脆弱;地下水位最低值与最高值一般均出现在7~9月,对生态环境具有强烈的影响。[结论]根据对塔里木河流域地下水位的监测预警,为了更加有效地保护塔里木河流域地下水,要处理好流域地下水开发、保护与生产、生态用水之间的关系,提高用水效率,禁止开荒扩大生产,严格管理地下水开采,保护好地下水水质,加大对流域下游的生态输水,逐步恢复下游生态环境。     

The role of common pool problems in irrigation inefficiency: a case study in groundwater pumping in Mexico

Groundwater depletion is a serious problem in Mexico. Several policy alternatives are currently being considered in order to improve the efficiency of irrigation water use so that extraction of groundwater is diminished. An understanding and quantification of different sources of inefficiency in groundwater extraction is critical for policy design. Survey data from a geographically extensive sample of irrigators is used to gauge the importance of common pool problems on input‐specific irrigation inefficiency. Results show that mechanisms of electricity cost sharing implemented in many wells have a sizable impact on inefficiency of irrigation application. Moreover, irrigation is very inelastic to its own unitary cost. Therefore, results suggest that policies aimed at eliminating electricity cost‐sharing mechanisms would be significantly more effective than electricity price‐based policies in reducing irrigation application. Results also show that well sharing does not affect groundwater pumping significantly, suggesting either a limited effect of individual pumping on water level or absence of strategic pumping by farmers sharing the wells.     

The relationship between land use and surface water resources in the UK

Land use and water resources are inextricably entwined. The need to protect the quantity and quality of water resources can impact potential land uses and land management practices, while water availability is a pre-requisite for land uses requiring irrigation. Land use and land management changes impact on water resources for example through changes in catchment yields, infiltration rates, dissolved organic carbon and nutrient transfers. While there is no absolute shortage of water resources across the UK as a whole, spatial and temporal variations already result in water stress across much of the south and east of England during dry summers. In the future, water stress is expected to become more widespread in response to population growth, increasing environmental protection and climate change. Surface water quality is reported to be improving at present, though there are doubts as to the adequacy of the monitoring coverage. Climate change is likely to adversely affect surface water quality, with less dilution in summer and more extreme rainfalls in winter leading to increased erosion and pollution. To conserve usable water resources, land uses which increase evapotranspiration or rapid runoff should be discouraged, particularly in the south and east, and there need to be continuing efforts to maintain good chemical water quality in rivers and groundwater. Water resource constraints will limit opportunities to use irrigation as a counter to climate change, and will influence where irrigated production can be located.     

Climate change impacts on investment in crop sowing machinery*

A model of investment in crop sowing machinery is applied to wheat production under current and projected climatic conditions at several locations in south‐western Australia. The model includes yield responses to time of sowing at each location given current and projected climatic conditions. These yield relationships are based on wheat growth simulation modelling that in turn draws on data from a down‐scaled global circulation model. Wheat price distributions and cost of production data at each location, in combination with the time of sowing yield relationships are used to determine a farmer's optimal investment in crop sowing work rate under each climate regime. The key finding is that the impacts of climate change on profit distributions are often marked, yet mostly modest changes in investment in work rate form part of the profit‐maximising response to climate change. The investment response at high versus low rainfall locations mostly involves increases and decreases in work rates, respectively. However, changes to investment in work rate within a broadly similar rainfall region are not always uniform. The impacts of climate change on investments in work rate at a particular location are shown to require knowledge of several factors, especially how climate change alters the pattern of yield response to the time of sowing at that location.     

Yield quality and irrigation with saline water under environmental limitations: the case of processing tomatoes in California

Irrigation with saline water has a positive impact on some quality indices of processing tomatoes, but with concomitant reductions in output quantity. This article studies the impact of the trade‐off between these two factors on optimal water management under waterlogging and costly drainage‐disposal conditions. The focus is on the content of total soluble solids as a quality measure affecting prices paid by California processors to tomato growers. A function relating quality to water and salinity applications and a quality hedonic‐price function are estimated and introduced into a static, field‐level mathematical programming model. The model calculates optimal water management under environmental regulations associated with drainage disposal in California. Findings indicate that only when the quality effect is taken into account does blending fresh surface‐water with saline drain‐water become an optimal strategy. Management and policy implications on the regional scale are discussed.     

Spot water markets and risk in water supply

Water availability patterns in semiarid regions are typically extremely variable. Even in basins with a highly developed infrastructure, users are subject to unreliable water supplies, incurring substantial economic losses during periods of scarcity. More flexible instruments, such as voluntary exchanges of water among users, can help users to reduce risk exposure. This article looks at the effects of spot water markets on the economic risk caused by water availability variations. Our theoretical and empirical risk analyses are based on the random profits of water users. Profit probability density functions are formally and graphically characterized for both water sellers and buyers under several possible market outcomes. We conclude from this analysis that, where water supply is stochastic, water markets unambiguously reduce both parties' risk exposure. The empirical study is conducted on an irrigation district in the Guadalquivir Valley (Southern Spain), where there is a high probability of periods of extreme water scarcity. Water demand functions for the district representative irrigators and a spatial equilibrium model are used to simulate market exchanges and equilibrium. This programming model is combined with statistical simulation techniques. We show that the profit probability distribution of a representative irrigator is modified if water exchanges are authorized, leading to risk reductions. Results also indicate that if the market were extended to several districts and users that are subject to varying hydrological risk exposure, extremely low‐profit events would be less likely to occur. In sum, we show that exchanging water in annual spot markets can reduce farmers' economic vulnerability caused by water supply variability across irrigation seasons. These results support the water policy reform carried out in Spain in 1999 to allow for voluntary water exchanges among right holders.     

Agriculture and climate change in global scenarios: why don't the models agree

Agriculture is unique among economic sectors in the nature of impacts from climate change. The production activity that transforms inputs into agricultural outputs involves direct use of weather inputs (temperature, solar radiation available to the plant, and precipitation). Previous studies of the impacts of climate change on agriculture have reported substantial differences in outcomes such as prices, production, and trade arising from differences in model inputs and model specification. This article presents climate change results and underlying determinants from a model comparison exercise with 10 of the leading global economic models that include significant representation of agriculture. By harmonizing key drivers that include climate change effects, differences in model outcomes were reduced. The particular choice of climate change drivers for this comparison activity results in large and negative productivity effects. All models respond with higher prices. Producer behavior differs by model with some emphasizing area response and others yield response. Demand response is least important. The differences reflect both differences in model specification and perspectives on the future. The results from this study highlight the need to more fully compare the deep model parameters, to generate a call for a combination of econometric and validation studies to narrow the degree of uncertainty and variability in these parameters and to move to Monte Carlo type simulations to better map the contours of economic uncertainty.     

The mountain environment,a driver for adaptation to climate change

The mountain environment is perceived today by vine-growers as a strong structural constraint. Yet in the current context of climate change, in which we turn to genetics, irrigation or innovation in cultural practices to maintain production quality, could the mountain environment emerge as a solution for adapting to climate change in vine-growing? Here we explore the role of cooperative policies that may be deployed on the territorial scale, using an agent-based model. Our model was based on the viticulture of the Banyuls–Collioures AOC area, which is characterized by small-scale vine-growers and marked by widespread involvement in cooperative systems. The simulation results showed an important role of cooperative policies not only to conserve narrow production window and required vine quality, but also in respect of the emblematic landscape structure. These results should foster vine-growers to strengthen their cooperatives and adequately use these organizations to mitigate future climate change impacts.     

Coping with drought with innovative pricing systems: the case of two irrigation water management companies in France

In recent years, France has been facing particularly severe drought periods especially in summer. In a country where agriculture is the largest water user, some irrigation management companies have implemented innovative pricing systems to handle this situation. The objective of this article is to analyze the impact of these new management systems on farmers’ incomes, the revenue of the management companies, and the amount of water used. To do that, we develop a methodology using a stochastic model that simulates the representative farmer's optimal behavior in a context of climatic variability. An empirical application is made with a crop growth model and data collected from the Midi‐Pyrenees region. The results show that using these specific nonlinear pricing systems allow irrigation water managers to reduce the impact of drought on production. Moreover, the type of pricing implemented depends on the characteristics and capabilities of the water company. More particularly, these pricing systems can be used to anticipate agricultural water demand in order to avoid imbalance with water availability.     

Soil and water conservation technologies: a buffer against production risk in the face of climate change? Insights from the Nile basin in Ethiopia

This study investigates the impact of different soil and water conservation (SWC) technologies on the variance of crop production in Ethiopia to determine the risk implications of the different technologies in different regions and rainfall zones. Given the production risks posed by climate change, such information can be used by decision makers to identify appropriate agricultural practices that act as a buffer against climate change. Results show that SWC investments perform differently in different rainfall areas and regions of Ethiopia and that the effectiveness of technologies such as irrigation, fertilizer, and improved seeds often depends on whether these investments are coupled with SWC measures. These results underscore the importance of the selection of appropriate combinations of technologies and careful geographical targeting when promoting and scaling up SWC technologies for adaptation to climate change.     

Evaluating irrigation investments in Malawi: economy‐wide impacts under uncertainty and labor constraints

Irrigation expansion is critical to increase crop yields and mitigate effects from climate change in Sub‐Saharan Africa, but the low profitability has led to little irrigation investments in the region so far. Using an integrated modeling framework, we simultaneously evaluate the returns to irrigation arising from both economic and biophysical impact channels to understand what determines the profitability of irrigation in Malawi. Our results confirm that the returns to irrigation cannot cover the costs in Malawi. While labor‐intensive irrigation expansion leads to unfavorable structural change in the short‐run, the profitability hinges on low irrigated yields that fall far from expectations due to insufficient input use and crop management techniques. On the other hand, we find that the nonmonetary benefits of irrigation regarding higher food security, lower poverty, and reduced vulnerability to climate change make investments in irrigation worthwhile to improve the livelihoods of smallholders.     

基于OLI影像的乌裕尔河—双阳河流域土壤碱化反演研究

近年来受环境变化和人类活动的影响,土壤盐碱化是土地退化的表现之一。研究土壤盐碱化有利于改善现状,并且预防其加剧具有重要意义。土壤碱化的快速反演和及时监测,对乌—双河流域生态可持续发展有着重大意义。以Landsat-8OLI遥感影像与野外采样测定的170个样点土壤p H值和EC为数据基础,实验室内采集光谱,建立光谱反射率及其变换形式与土壤p H值和EC的相关分析,选择最佳敏感波段,利用线性回归分析建立基于OLI影像的乌裕尔河—双阳河流域土壤盐碱化反演模型,该模型的建立可为区域土壤碱化信息的提取及监测提供参考。