Meet Water Demand Research Articles

Modeling GCM and scenario uncertainty using a possibilistic approach: Application to the Mahanadi River, India

Climate change impact assessment on water resources with downscaled General Circulation Model (GCM) simulation output is characterized by uncertainty due to incomplete knowledge about the underlying geophysical processes of global change (GCM uncertainties) and due to uncertain future scenarios (scenario uncertainties). Disagreement between different GCMs and scenarios in regional climate change impact studies indicates that overreliance on a single GCM with a scenario could lead to inappropriate planning and adaptation responses. This paper focuses on modeling GCM and scenario uncertainty using possibility theory in projecting streamflow of Mahanadi river, at Hirakud, India. A downscaling method based on fuzzy clustering and Relevance Vector Machine (RVM) is applied to project monsoon streamflow from three GCMs with two green house emission scenarios. Possibilities are assigned to all the GCMs with scenarios based on their performance in modeling the streamflow of the recent past (1991–2005), when there are signals of climate forcing. The possibilities associated with different GCMs and scenarios are used as weights in computing the possibilistic mean of the CDFs projected for three standard time slices 2020s, 2050s, and 2080s. The result shows that the value of streamflow at which the CDF reaches 1 reduces with time, which shows the reduction in probability of occurrence of extreme high flow events in future. Historic record of monsoon streamflow of Mahanadi river also shows similar decreasing trend, which may be due to the effect of high surface warming. Reduction in Mahandai streamflow is likely to pose a major challenge for water resources engineers in meeting water demands in future.

Water for irrigation or hydropower generation?—Complex questions regarding water allocation in Tanzania

The need for achieving efficient, equitable and sustainable use of water resources to meet water demands of different sectors is pressing, particularly in areas where water resources are dwindling. Along with this is the quest for having a good understanding of the value of water in its different uses. Using a simplified model derived from the residual imputation approach (the Change in Net Income Model) we assess the value of water in irrigated paddy and hydropower generation in the Great Ruaha River Catchment (GRRC) in Tanzania. The estimated productivity of water (PW) in irrigated paddy ranges from 0.059 to 0.250 kg/m 3 (for withdrawn water) and 0.126 to 0.265 kg/m 3 (for consumed water). The PW in hydropower generation is estimated to range from 0.45 to 1.68 kWh/m 3. In monetary terms the value of water in irrigated paddy is estimated at 15.3 Tanzanian shilling (Tsh)/m 3 (for water withdrawn) and 0.19 Tsh/m 3 (for water consumed). The values of water for hydropower generation are relatively higher than for irrigated paddy, ranging from 59 to 226 Tsh/m 3. Yet, irrigated paddy also supports livelihoods of about 30,000 agrarian families in the GRRC, with gross revenue of about Tsh 15.9 million per annum and GRCC paddy contributes about 14–24% of national rice production. We conclude that understanding the value of water in its alternative uses is key to fostering informed debate on water management and allocation, identifying the basis for making ‘agreeable’ trade-offs, the potential for improvement and creating linkages with water allocation options particularly in agricultural-based economies, where agriculture competes with other sectors and where water re-allocation decisions may involve large transfers of water from the sector generating the highest pro-poor returns (agriculture for this case) to the sectors generating the highest economic returns (hydropower generation and industrial uses).

A general water supply planning model: Evaluation of decentralized treatment

Increasing population, diminishing supplies and variable climatic conditions can cause difficulties in meeting water demands; especially in arid regions where water resources are limited. Given the complexity of the system and the interactions among users and supplies, a large-scale water supply management model can be useful for decision makers to plan water management strategies to cope with future water demand changes. It can also assist in deriving agreement between competing water needs, consensus and buy-in among users of a proposed long-term water supply plans. The objective of this paper is to present such a general water supply planning tool that is comprised of modular components including water sources, users, recharge facilities, and water and wastewater treatment plants. The model is developed in a system dynamics simulation environment that helps users easily understand the model structure. The model was applied to a realistic hypothetical system and simulated several possible 20-year planning scenarios. In addition to water balances and water quality analyses, construction and operation and maintenance of system components costs were estimated for each scenario. One set of results demonstrates that construction of small-cluster decentralized wastewater treatment system could be more economical than a centralized plant when communities are spatially scattered or located at steep areas where pumping costs may be prohibitive.

Optimal Allocation of Water Resources in Guangzhou City, South China

Based on the theory of decompose-coordination for large-scale systems, a systematic optimal operation model with multi-objective programming is developed for optimal allocation of water resources in Guangzhou City, South China. The methods of hierarchical analysis and step by step toleration obligation are used in the process of coordination through the sub-systems. Through the integrated regulation of 13 reservoirs and 6 main rivers and the regional watersheds, estimated water amount for dry year (P = 97%) is distributed optimally to 14 water resource units to meet water demand in the year 2020. Water shortage due to lack of runoff and insufficient water supply projects is analyzed. The scheme of water allocation within seven water resource districts is put forward to match the sustainable balance of water supply to water demand in Guangzhou City.

Californian cities use membranes to meet water demand

Major Californian cities are now realizing the benefits of using membrane-based filtration technology to help them meet the growing demand for clean water. Here we look at some recent projects.

Man-made lakes in Mediterranean semi-arid climate: the strange case of Dr Deep Lake and Mr Shallow Lake

The lack of any protection against eutrophication is progressively compromising the water quality of Sicilian reservoirs. These water bodies provide the population with an adequate supply of drinking water and support most of the irrigation requirements of local agriculture. Moreover, they respond to the Mediterranean climate, with sequential, seasonally predictable events of flooding and drying and whose intensity varies markedly between years. As a consequence of summer drought and the policy to meet water demand throughout the season, the reservoirs experience massive dewatering, resulting in a reduction in the spring storage volume of 90%. Thus, they start the hydrological season as water bodies deep enough to form stable stratification but a thermocline has generally disappeared by the middle of summer and, as a consequence of the intense drawdown, they are transformed into shallow water bodies. This dual behaviour, driven by a progressive and conspicuous depth decrease, interferes with nutrient and phytoplankton dynamics, enhancing eutrophication phenomena and contributing to the selection of planktic cyanobacteria that are potentially dangerous to human health.

Potential for Blue-Gray Water Trade-offs for Irrigation in Small Towns of Pakistan: A Case Study of Farmers’ Costs and Benefits in Haroonabad

The growing demand and the competition for fresh water in various sectors suggest that the irrigated agriculture will have to release freshwater for more important and valuable uses. This implies that other options would need to be identified to meet water demands for agriculture. Meeting irrigation requirements through non-conventional water sources is one of the options for agricultural uses. Gray water use for irrigation, a pervasive practice in urban and peri-urban areas of many developing countries, could be one of the solutions. The debate on wastewater irrigation from an environmental point of view is already on, focussing more on human and environmental “safety” aspects. The “value” aspect of the wastewater irrigation remains neglected, however. The irrigation users of untreated wastewater in many parts of the world had already traded off and revealed their preference for gray over blue water decades ago, when the water supply systems in towns and cities were set up. Why they would do it despite the high environmental and health risks associated with its use needs an answer. The paper documents the costs and benefits of wastewater irrigation from users’ point of view, and assesses the potential for real blue water savings in a small town setting in the southern Punjab, Pakistan. The data presented in the paper suggest that wastewater irrigation does lead to blue water savings, and it is profitable for farmers. While its potential is not fully exploited, more focus on appropriate approaches to physical and institutional aspects of wastewater disposal planning and management could make wastewater irrigation more productive, profitable, and safe for individuals as well as for the society as a whole.

Wastewater reuse in Italy

In many parts of Italy, particularly in the South, it has become ever more difficult to meet the water demand. The recent years of drought and the constant increase of water demand for the civil sector have made irrigation supply more problematic. Wastewater reuse could represent a viable solution to meet water demand. The focus of this paper is on the regulation problems, hampering the development of wastewater reuse for irrigation, and on the potentials for reuse, particularly in Southern Italy. Planned exploitation of municipal wastewater could help meeting the irrigation water demand particularly in Southern Italy, where farmers have been practising uncontrolled wastewater reuse for a long time. In Northern and Central Italy, where available water resources generally meet water needs for different purposes, wastewater reuse could play an important role in controlling the pollution of water bodies. Despite the fact that Italian legislation is extremely strict and outdated, for several years in some regions, such as Sicily, wastewater reuse systems have been in operation; furthermore, several projects of wastewater reuse are currently in progress.

Alfalfa rapidly remediates excess inorganic nitrogen at a fertilizer spill site.

By 19%, standard remediation techniques had significantly reduced the concentration of nitrate nitrogen (NO3- -N) in local ground water at the site of a 1989 anhydrous ammonia spill, but NO3- -N concentrations in portions of the site still exceeded the public drinking water standard. Our objective was to determine whether local soil and ground water quality could be improved with alfalfa (Medicago sativa L.). A 3-yr study was conducted in replicated plots (24 by 30 m) located hydrologically upgradient of the ground water under the spill site. Three alfalfa entries ['Agate', Ineffective Agate (a non-N2-fixing elite germplasm similar to Agate), and MWNC-4 (an experimental germplasm)] were seeded in the spring of 1996. Corn (Zea mays L.) or wheat (Triticum aestivum L.) was seeded adjacent to the alfalfa each year. Crops were irrigated with N-containing ground water to meet water demand. During the 3-yr period, about 540 kg of inorganic N was removed from the aquifer through irrigation of 4.9 million L water. Cumulative N removal from the site over 3 yr was 972 kg N ha(-1) in Ineffective Agate alfalfa hay, compared with 287 kg N ha(-1) for the annual cereal grain. Soil solution NO3- concentrations were reduced to low and stable levels by alfalfa, but were more variable under the annual crops. Ground water quality improved, as evidenced by irrigation water N concentration. We do not know how much N was removed by the N2-fixing alfalfas, but it appears that either fixing or non-N2-fixing alfalfa will effectively remove inorganic N from N-affected sites.

Prediction of the Effect of Pumping on Al-Wasia Well Field

Al-Wasia Aquifer is one of the major aquifers in Saudi Arabia which is found in the Central and Eastern regions of the country. Al-Wasia well field (62 wells) has been in operation since 1981 to supply water to Riyadh. It is located about 110 km north-east of Riyadh close to Riyadh-Dammam Highway. Amounts and rates of pumping from the well field have been changing during the last few years depending on water demand of Riyadh. The operation of the well field is examined under three different pumping stresses. The choice of a pumping pattern is according to the expected amount of pumped water from the well field to meet water demand of Riyadh. A two-dimensional regional ground water flow model (REGNLGW) is utilized to predict the expected water/piezometric levels in the well field due to the different pumping patterns up to the year 2010. The results of the simulation of the different pumping patterns show that piezometric level, in the year 2010, will not reach the critical depth of 300 m below ground surface. This depth is assumed critical because it is economically infeasible to extract water from depths greater than 300 m.

Groundwater–Surface Water Management With Stochastic Surface Water Supplies: A Simulation Optimization Approach

A new simulation optimization model for groundwater–surface water management identifies efficient strategies for meeting water demand and controlling a regional water quality problem, while accounting for varying availability of surface water supplies. Optimal values of model variables are computed for ranges of surface water availability. Expected groundwater levels are computed using a response function approach, which incorporates a probability for each hydraulic stress. Three objective functions are considered: (1) minimize need for supplemental water, (2) minimize imposed water use reductions, and (3) minimize changes from current pumping patterns. The model imposes constraints on expected groundwater levels, expected hydraulic gradients (surrogates for controlling contaminant transport), capacities of pipeline and recharge facilities, and water demand requirements. Capacity and demand constraints must be met every year for all possible surface water conditions. Application to the Santa Clara–Calleguas Basin in southern California indicates that a large quantity of supplemental water or significant pumpage reductions, particularly in the lower aquifer, may be required to control seawater intrusion with current facilities. Supplemental water would be delivered directly to users through pipelines and artificially recharged. Results also indicate that the current artificial‐recharge program has been valuable and that construction of new artificial‐recharge facilities might be beneficial. It should be noted that local agencies are currently developing several potential sources of supplemental water. Monte Carlo simulations yield estimates of the reliability of gradient constraints in controlling advective transport and the likelihood that water level constraints will be violated.

WATER MARKETS AND DECENTRALIZED WATER RESOURCES MANAGEMENT: INTERNATIONAL PROBLEMS AND OPPORTUNITIES1

ABSTRACT: Because of its importance and the perceived inability of private sector sources to meet water demands, many countries have depended on the public sector to provide water services for their populations. Yet this has resulted in many inefficient public water projects and in inadequate supplies of good quality and reliable water. Decentralization of water management, including the use of water markets, cannot solve all of these water problems, but it can improve the efficiency of water allocation. When given adequate responsibility and authority, water user associations have effectively taken over water management activities at a savings to tax payers. Moreover, water markets add the potential benefit of improving water efficiency within a sector as well as providing a mechanism for reallocating water among sectors. The key question involves developing innovative mechanisms for reducing the transaction costs of organizing water users and of making water trades. Water rights need to be established which are recorded, tradable, enforceable, and separate from land if markets are to operate effectively. Also, institutions are needed that effectively resolve conflicts over water rights, including third party impacts and water quality concerns.

WESTERN WATER RESOURCES: THE DESERT IS BLOOMING, BUT WILL IT CONTINUE?1

ABSTRACT: The arid Southwest of the United States is confronted with increasing water demands and a limited resource. Past efforts to meet water demand have been directed toward development of scarce water resources. While development programs have been successful in stretching available supply, few feasible development options remain. Furthermore, heavy water utilization has affected water quality within drainage basins. It seems likely that water management will play a much more significant role in water resource allocation in the future. This paper will examine water development activity in the Southwest to date. Attention will be given to several of the problems that have arisen. The paper will then examine water management options. Particular attention will be given to water management options being implemented in the State of Arizona.

Inter-basin Water Transfer: Ecological Concerns

The concept of transferring water from one river basin to another has evolved over centuries as a useful means of meeting water demands. However, such projects have the potential for serious ecological impacts, including introduction of nonindigenous organisms, changes in water quality and hydrologic regimes, and alteration of habitat. Although limited progress has been made in the last 20 years regarding our understanding of site-specific ecological consequences of inter-basin water transfer, research to date is inadequate for assessment of water transfer impacts. It is imperative that we develop coordinated research methodologies to be incorporated into the planning and evaluation of inter-basin water transfer projects.

Skid mounted mobile brackish water reverse osmosis plants at different sites in Kuwait

It has been realised that the storage of water to be used during emergency cases will not be sufficient to meet water demand if emergency cases lasted for an unexpected period. This lead to the idea of having small mobile Reverse Osmosis desalination units installed at various sites in Kuwait and to serve essential communities such as hospitals and army camps. Consequently, the authors set specifications for the supply of thirteen Skid Mounted Mobile Brackish Water Reverse Osmosis units of capacity 250,000 IGPD, each. The units are identical in all aspects and utilizing low pressure membranes. This paper describes the operation, maintenance, performance and unit water cost of one of the units during one year continuous operation.

Analysis of reservoir storage reallocations

A hydrologic and economic evaluation procedure is presented for analyzing proposed reallocations of reservoir storage capacity between flood control and municipal and industrial water supply. The generalized procedure consists of evaluating the risks and consequences of failing to prevent flooding and failing to meet water demands. The central thrust of the procedure is the estimation of average annual economic losses associated with alternative allocations of storage capacity between purposes. Average annual flood losses are computed using the damage-frequency method. Average annual water-supply losses are estimated by developing a water shortage versus economic loss function which is then applied to water shortages computed by a hydrologic simulation. The water shortage versus loss function reflects emergency demand management and supply augmentation measures. Average annual water-supply losses are estimated for a given demand level. Long-term demand management strategies are reflected in the water demand projections.

Multiple-Use Projects in Development of Water Resources

The author reflects on water development projects and concludes with a list of objectives for meeting water demands that are projected to double over the next 20 years.