Uncertainty Of Water Supply Research Articles

Integrated and adaptive governance of water resources: the case of South Africa

Climate change and its impact on water resources have become a reality in many parts of the world. Uncertainties in water supply as well as the gradual and abrupt change in water availability are increasing. To maintain the sustainability of the water sector, its ability to adapt to unforeseen events needs to increase. Making adaptation an integral part of the governance of water resources will thus be one of the major future challenges for the water sector. This paper focuses on how far Integrated Water Resource Management (IWRM), the guiding concept of water management and governance, is able to address these challenges and which additional features would be required for increasing the adaptability of water governance and management. In the empirical part of the paper, South African water legislation and its adaptability to the challenges of climate change is scrutinised. The paper finds that IWRM offers a number of entry points for increased adaptability. However, the IWRM concept should be complemented with features of adaptive governance such as polycentric, redundant and flexible governance structures to be better prepared for unforeseen events. It is concluded that the features of IWRM and adaptive water governance comprise a number of synergies and trade-offs, which play out differently in different combinations and contexts. The paper outlines the need for further empirical research on these trade-offs as well as on the appropriate degree of features such as participation, flexible institutions and redundancy.

Spatial–temporal changes of precipitation structure across the Pearl River basin, China

Using daily precipitation data covering 1960–2005 from 42 stations across the Pearl River basin, precipitation indices, defined by annual total precipitation amount, annual total rainy days, annual precipitation intensity and annual mean rainy days, are analyzed using the modified Mann–Kendall trend test method. Results indicate that: (1) decreasing precipitation is found mainly in the middle and upper Pearl River basin. However, a decreasing number of rainy days is detected almost over the entire basin. Thus, the Pearl River basin is characterized by increasing precipitation intensity, particularly in the middle and the eastern parts of the basin; (2) the occurrence and fractional contribution of wet periods (WPs) with longer durations are decreasing in recent decades and WPs with shorter durations, e.g., 2–5 days are tending to be predominant in recent decades with increasing total precipitation amount. Frequencies of shorter WPs with increased total precipitation amount can be expected, which can easily trigger occurrence of floods and droughts; (3) heavy precipitation is easy to occur in WPs with shorter durations which may further corroborate the intensified precipitation process in the Pearl River basin, particularly in the lower part. Reduction of water supply from the upper Pearl River basin due to decreased precipitation and higher risk of floods and droughts in the lower basin will increase uncertainty of water supply in the lower basin and hence pose new challenges for water supply and water resources management under the influence of climate change and human activities, such as increasing water demand as a result of booming socio-economy and fast population growth.

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

Abstract 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.

Abstracts of Award‐Winning Theses

Abstracts of Award‐Winning Theses

확률제약 계획모형법을 이용한 농업용수의 경제적 가치 평가

본고는 경제적 최적화모형인 확률제약 계획모형법을 이용하여, 농업용수 부존량 감소에 따른 농업이윤의 감소분을 계측하고 이를 통해 농업용수의 경제적 가치를 분석하고자 한다. 이를 위해 국가 전체 농업자원배분을 최적화 모형으로 구축하고, 농업용수를 포함하는 자원부존제약조건과, 각 상품의 가격이 형성되는 시장조건, 국제무역 및 관련정책변수의 영향들을 반영하고, 용수의 경우 그 이용량이 연도별로 불안정할 수 있다는 것까지 반영한다. 농업용수감소량이 농업부문 이윤에 미치는 영향을 시나리오를 주어 분석하면, 농업용수의 톤당 경제적 가치는 <TEX>$303{\sim}1,093$</TEX>원/<TEX>$m^3$</TEX>의 분포를 가지는 것으로 나타난다. 동일한 양의 용수량이 줄어들더라도 용수의 공급이 불안정할수록 경제적 가치 손실이 크며, 아울러 많은 양의 용수손실이 발생할수록 경제적 손실이 커 용수감소의 한계피해는 용수감소량의 증가 함수인 것으로 파악된다. This study estimates the value of irrigation water in Korea using an economic programming model that is constructed with all the resource endowment constraints, technology restrictions and policy variables. The variability and uncertainty of water resource endowment are incorporated into the model through the chance-constrained technique. Solving the profit maximization problems with gradually reduced water endowments, we derive a series of shadow values of irrigation water. It has been found that uncertainty in water supply raises the damage from water loss, and the marginal damage increases in water loss.

Managing Water to Protect Fish: A Review of California’s Environmental Water Account, 2001–2005

The Sacramento-San Joaquin Delta, the landward reach of the San Francisco Estuary, provides habitat for threatened delta smelt, endangered winter-run Chinook salmon, and other species of concern. It is also the location of huge freshwater diversion facilities that entrain large numbers of fish. Reducing the entrainment of listed fishes into these facilities has required curtailment of pumping, reducing the reliability of water deliveries. We reviewed the first 5 years (2001-2005) of the Environmental Water Account (EWA), a program instituted to resolve conflicts between protecting listed fishes and providing a reliable water supply. The EWA provided fishery agencies with control over 0.2-0.4 km(3) of water to be used for fish protection at no cost to users of exported water, and fish agencies guaranteed no disruption of water supply for fish protection. The EWA was successful in reducing uncertainty in water supply; however, its contribution to the recovery of listed fishes was unclear. We estimated the effectiveness of the EWA to be modest, increasing the survival of winter-run Chinook salmon by 0-6% (dependent on prescreen mortality), adult delta smelt by 0-1%, and juvenile delta smelt by 2-4%. Allocating EWA water for a single life stage of one species could provide larger gains in survival. An optimally allocated EWA of equal size to the median of the first 5 years could increase abundance of juvenile delta smelt up to 7% in the springs of dry years. If the EWA is to become a long-term program, estimates of efficacy should be refined. If the program is to be held accountable for quantitative increases in fish populations, it will be necessary to integrate scientific, possibly experimental, approaches.

Rainfall Insurance: A Promising Tool for Drought Management

Diverse and complex water management systems have been created in many areas of the world to manage the risk of drought. The primary challenge is the inherent uncertainty of water supply and demand over time, which makes the process of correctly allocating water rights annually a difficult and costly task. As a result, risk averse water authorities make overly conservative estimates of water supply. This paper introduces the use of a rainfall index contract as a tool to improve drought management. An irrigation district in New South Wales, Australia, is used as an illustration of the concept.

Applying Technology for Sustainable Water Management: The Pratt Water Experience

This paper is about sustainability in water management from a business perspective. The idea of sustainability has evolved over the centuries. It emerged after the era of super abundance, through the needs of humans in community, to the protection of the commons, and the wider environment. Regulation by government is a relative latecomer, in response to third party scrutiny of resource mismanagement. However, the idea of sustainability has also been embraced, and put into practical effect, through the passion and vision of some business leaders. Richard Pratt has built an entire global business on the foundation of sustainability—through recycling and closed-loop principles. Richard Pratt's vision for sustainability in Australia's water management has spawned Pratt Water, which is shortly to report on an intensive study into business investments to save and sustain water resources in the Murrumbidgee Valley in NSW, Australia.The Murrumbidgee River carries 4400 gigalitres (GL) of water each year for 1700 km between Canberra and Balranald. About half this is diverted for irrigated agricultural production purposes. The Murrumbidgee Valley Water Efficiency Feasibility Project seeks to answer key water efficiency questions that will drive new investment, save water and enhance the prospects for regional communities. The current Murrumbidgee Valley's water supply businesses revealed that they cannot support the new investments required to allow them to operate at best practice in terms of water efficiency. The water business balance sheet shows that water is being lost from the River Valley system, and no-one confidently knows where it is going, or at what opportunity cost it is being lost.Pratt Water has found that, Valley-wide, about 70 GL are lost to evaporation from the open water, and a further 170 GL, or around 8% of allocations, are lost on or near farms each year. Much larger volumes (over 500 GL/year) are simply unaccounted for. Problems with measurement and monitoring of river and offtake flows contribute to water supply uncertainty. Measurement variances of up to 33% mean that no-one can confidently ‘sign off’ on the water business accounts.Pratt Water undertook a detailed economic ranking to establish the costs and benefits of fixing the leaks or otherwise capturing the system's water losses and putting them to new productive use. Using the saved water on higher values crops, and/or including saving costs as part of the overall water supply charges are two ways of achieving better water use for the entire community's benefit.The Pratt Water Murrumbidgee project identified additional or new market-based production opportunities within the valley to both generate water savings through best practice (compared to existing activities) and to utilize water saved through other interventions. On this analysis, valley-wide farm gate income could rise by over $100 m/year, which represents about a 20% increase on current economic output. Pratt Water also identified and trialled ways of dramatically lowering the cost of irrigation water delivery, while at the same time improving water use efficiency. This included a new woven, plastic-coated flume pipe which cost 72% less than conventional delivery infrastructure and saved 30–40% of the irrigation water.Better management of high summer river flows was also addressed. Solutions included above-ground and below-ground water storages. An aquifer storage and recovery scheme was identified which could provide additional water for as little as $62/ML, whilst providing a means of managing the excessive drawdown in the lower valley's groundwater profile. The team also characterized the ecological assets of the valley and identified ways of supplying the right water at the right time and in an economically feasible way to sustain those environmental resources.As the present drought has starkly underlined, water delivery choices, in terms of quality, quantity and timing, are also becoming critical issues for the entire community. While demand for water grows in a supply-constrained system, water users are demanding cost competitiveness in the supply and delivery of that water in the face of increased market competition for the goods they are producing. Pratt Water is showing the needed leadership for the private sector to provide business-led solutions to tackle this crucial water sustainability challenge.

Modeling irrigated agricultural production and water use decisions under water supply uncertainty

Farmers make joint water and land use decisions for economic purposes based in part on water availability and reliability. A two‐stage economic production model is developed to examine the effects of hydrologic uncertainty and water prices on agricultural production, cropping patterns, and water and irrigation technology use. The model maximizes net expected farm profit from permanent and annual crop production with probabilistic water availability and a variety of irrigation technologies. Results demonstrate effects of water availability, price, and reliability on economic performance, annual and long‐run cropping patterns, and irrigation technology decisions. Variations in water price and availability affect the desirability of different irrigation technologies. Increased water supply reliability can raise the probability of higher economic returns and promote more effective use of water for permanent crops. Such economic benefits can be compared to costs of operational changes and programs to increase water supply reliability for agricultural areas.

The social response to irrigation: An Indian case study1

Because canal irrigation is a resource which has to be managed collectively, it is said to be an important determinant of the forms of social organisation of villages which benefit from it. This paper examines this argument with evidence from villages in a Southern Indian district. It concludes that there is a relationship between the degree of corporate organisation and the scarcity and uncertainty of water supply, but that the starkness of the relationship is often softened by a number of other relevant factors