Factors Affecting Patterns of Water Use
The history of predicting water use and related economic activity, population growth, and other variables of importance to water and economic planners shows that precise predictions are often incorrect. Difficulties arise because there are many unknown and poorly defined variables and because people are ingenious in their adaptations to change. Although predictions, projections, and scenario building rarely provide an adequate basis for planning by themselves, they may be useful in identifying and analyzing different options. Thus, many of the factors that are likely to affect future water use can be identified.
The 1996 UN report assessing the freshwater resources of the world concludes that "water use has been growing at more than twice the rate of the population increase during this century and already a number of regions are chronically water short. About one-third of the world's population lives in countries that are experiencing moderate to high water stress, resulting in part from increasing demands fueled by population growth and human activity. By 2025, as much as two-thirds of the world population would be under stress conditions" (UN, 1996). It is recognized that areas that are short on water may in effect import it from other areas when they import food or energy or manufactured products that require water inputs.
The peoples of the study area will almost assuredly live under conditions of significant water stress during the immediate future. Barring completely unforeseen events, the population of the region is likely to grow, possibly very rapidly. Moreover, the region will likely continue to
develop economically, and such economic growth could be substantial in Jordan and the West Bank and Gaza Strip. The twin phenomena of population and economic growth will place increasing pressure on the already limited water supplies of the region. The region's success in managing this intensifying water problem will largely be a matter of how it identifies and accounts for all of the many factors that determine and influence water use.
This chapter reviews the factors that are likely to influence future water use, giving special consideration to practices that may be amenable to some degree of change. The chapter's discussion begins with the difficulties of projections and the problems associated with identifying specific disparities between water supply and demand.
Projected Supply-Demand Disparities and Water Resources Planning
Water resource planners frequently focus on identifying potential gaps between water demand and water supply at some future date. Detailed plans are then developed to ensure that supplies are brought into balance with anticipated demands, thereby eliminating the gap. Such plans typically include projections of anticipated levels of water use based on population growth, per capita and per hectare water use, and other variables that affect demand. These estimates of future use are then compared with existing levels of available water supplies, and the time when a ''gap" or disparity between anticipated levels of use and existing levels of supply is identified. Based on the size and timing of this gap, measures and actions are then identified to close the gap and bring supplies into balance with the expected demands. There are many examples of this planning methodology (California Department of Water Resources, 1994), including many of the water planning analyses for the study area (see, for example, CES Consulting Engineers and GTZ, 1996).
The committee believes that water planning approaches that initially focus on emerging gaps between supply and demand are flawed. They are based on projections that, however well informed, often ignore the considerable uncertainty surrounding future levels of water use; and more generally, such plans are always based on a significant number of assumptions, many of them untested and unstated. To the extent that water availability determines population and economic growth, projections can become self-fulfilling prophesies. By contrast, where economic and population growth are only weakly determined by the availability of water, overly optimistic growth projections may lead to investment in excess water supply capacity, the costs of which must be borne, regardless of whether the water is used. In circumstances characterized by significant
levels of uncertainty, plans that are both adaptive and flexible may be desirable. The uncertain prospect of global environmental change, for example, would appear to call for flexible responses, permitting regions to adapt reasonably quickly to changes in climatic patterns as they emerge (Vaux, 1991).
Many assumptions in the traditional analyses are unstated or have not been subject to careful examination. Frequently, plans are based on the assumption that current levels and patterns of water use are optimal, irrespective of the costs of maintaining them in the face of population and economic growth. The role of prices in rationing the quantities of water used is rarely considered, since most such studies are premised on the unstated notion that real or nominal prices for water should remain constant. Additionally, planning based on the analysis of gaps frequently fails to identify the full range of adaptive mechanisms through which growth in water demands can be accommodated. Thus, such studies have often been done for the sole purpose of justifying the "need" for public financing of additional facilities, even though other less expensive means for balancing water supply and demand may have been available. It is only recently that such plans have included significant consideration of various options for managing water demand (see, for example, Berkoff, 1994).
The ultimate issue for planning, of course, is not closing any gap in the most literal sense: the quantity of water supplied always equals the quantity demanded or used. It is not physically possible for an individual or population to use more water than is actually available. The issue is rather that the amount of water desired or needed for many purposes may exceed available supplies. In many Middle East households, water supply is severely restricted for some or all of the time, and such restrictions may grow as economies and populations grow unless water delivery capacities can be increased. Where existing levels of water use are extremely low compared with the levels needed to avoid high economic and social costs, attention understandably focuses on closing the water supply "gap" between current and minimally acceptable levels of use. In addition, where current levels of supply include sources that cannot be sustained over the long-run—"mined" ground water, for example—it will not be possible to maintain a balance between supply and existing patterns of use indefinitely. Bringing demand and supply into balance in such cases requires reallocation among uses or the development of new supplies. Either action may entail substantial economic, social, or environmental costs.
The planning issue, then, is the identification of alternative options through which supply and demand can feasibly be balanced, the costs of achieving these various alternatives, and the amounts of water use and
allocations among sectors that each alternative allows. Any plan for managing water scarcity in the Middle East should identify the full range of alternatives for augmenting water supply and managing demand, provide estimates of the costs of each alternative, and identify and characterize alternative levels of water use where supplies and demands are in equilibrium.
In developing and assessing strategies to manage scarce water supplies, it will be important to identify the variables that have a large influence on the level of water use. It will be equally important to understand the extent to which these variables can be managed and controlled, or be changed by further research and development.
Factors that Affect Water Use
The quantities of water used in any activity are jointly determined by the supply of water available to support that activity and the demand for water in that activity. Both the supply and the demand for water are further determined by variables that tend to be location specific. Nevertheless, a number of overarching factors influence levels of water use independent of location. These factors will undoubtedly be critical in determining future levels of water use in the study area.
Population Numbers and Distribution
At the most fundamental level, water is needed to supply people's basic domestic needs, in quantities directly proportional to the number of people. Other uses of water include the various municipal, industrial, agricultural, environmental, and other uses described elsewhere in this report. The quantities of water used for these purposes are also related to some degree to the number and spatial distribution of people in the region, but these quantities are also affected by many other factors, discussed below. Finally, people residing in urban areas tend to have different patterns of water use, and they tend to use different quantities of water than people in rural or agricultural areas.
Trends in population growth and distribution are extremely difficult to predict. Currently, annual population growth rates in the study area are 3.6 percent in Jordan, about 3.1 percent in the West Bank and Gaza Strip, and about 2 percent in Israel. However, the growth and distribution of population has been strongly sensitive to events both within and outside the study area. For example, armed conflicts in the Middle East resulted in three waves of immigration to Jordan and changes in policies
in the former Soviet Union and its ultimate dissolution led to significant immigration to Israel. Although it appears quite likely that population in the study area will continue to grow over the next few decades, the rates and distribution of this growth are extremely difficult to predict accurately.
Technology and changes in technology may affect the availability or supply of water, demand for water and levels of water use. Industrialization, for example, typically increases the demand for water, at least initially. However, technological developments that permit users to economize on water—such developments as water-efficient indoor plumbing fixtures, closed-conduit irrigation systems like drip and microsprinkler systems, and computerized irrigation management techniques—frequently result in reductions in water use. Technical improvements that improve timing and lower costs of supply can also affect water use. For example, the construction of impoundment facilities permits control and regulation of runoff and allows more constant levels of supply. Over the last century, pumping technology improvements have made new sources of ground water available that previously could not be exploited because of their depth. On the other hand, failure to employ modern technology may mean lower quantities and higher costs of available supply.
While improvements in technology have sometimes dramatically increased the availability of water supplies, technology can also produce unwanted and unforeseen side effects. Some technology-induced or technology-influenced changes in water supply may be reversible only over time scales of thousands of years. For example, the construction of large dams (NRC, 1987, 1996), exploitation of ground water and irrigation practices (NRC, 1989) may alter water quality, regional hydrology, and water-dependent ecosystems in ways that are either impossible or prohibitively expensive to reverse on any reasonable time scale. Consequently, a complete assessment, including considerations of sustainability (and intergenerational equity), of the impacts of new and existing water supply technology should identify specifically the time domains over which the benefits and costs of the technology are likely to be borne.
Economic conditions, both within and outside the study area may affect water supply and demand. Recent declines in the world price for cotton have caused sharp declines in the potential profits from cultivation of irrigated cotton. In turn, this development has provided both the political
and economic impetus to reduce cotton plantations in Israel and replace those irrigated plantations with dryland agriculture, significantly reducing water demands. World energy prices also affect the quantities of water used by boosting the price of water that must be pumped or treated before it can be used. Changes in economic conditions also affect foreign trade in many ways whose implications for water use are not always easy to foresee. Finally, economic conditions within the region will affect water supply and demand by affecting the ability of water users to pay for water, as well as the ability of producers to purchase capital and labor for activities in many industries that may directly or indirectly affect water use, including agriculture.
Changes in environmental conditions can also significantly influence water supply and demand. Increased precipitation or decreased evapotranspiration are likely to augment water supplies and reduce the water demanded by irrigated agriculture. Increases in temperature or decreases in vegetated area or biological diversity are likely to diminish available supplies and increase the water demanded in many water using sectors. Water quality deterioration due to increased contamination levels reduces the available supply of water as surely as drought.
Changes in the environment can be directly or indirectly caused by human activities, or they can be (apparently) unrelated to human activity. For example, global climate change occurred long before humans or even living organisms inhabited the planet. Such change is likely to continue, but will be continued with global change caused by human activity. The human-induced global climate change may be pervasive and may have already occurred. Global change is likely to have significant or even profound impacts on regional water supplies and demands. However, current understanding of global climate patterns makes it very difficult to assess the impacts of such change regionally and therefore to predict how such critical variables as temperature and precipitation might change in the study area.
Discussions in this report also show how ecological conditions can affect water quality and quantity, and vice versa. Since the origins and mechanisms of these interactions are not always well understood, these changes are also hard to predict. However, the certainty that environmental change will occur suggests the need for flexible water management and allocation schemes for populations in the study area and elsewhere to respond to change as it occurs.
Instream and Withdrawal Uses of Water
In characterizing patterns of water use, one fundamental distinction is that between instream and withdrawal uses of water. The flowing or fleeting nature of water resources means that in many instances, certain uses of water do not impair its availability for further use. These uses are commonly termed instream: they do not notably alter the properties of the water nor thus the quality or quantity of water to serve subsequent uses. Examples of instream uses include most recreational uses, support of aquatic habitats and other environmental uses, navigation, and generation of hydroelectric power.
When water is withdrawn from a surface water body or from an aquifer it may be used either consumptively or non-consumptively. Consumptive uses occur when water is transformed from a state or location from which it can be used to one in which it cannot be used. Water used consumptively is not available for subsequent uses. Examples include uses such as irrigation, in which transpired water is evaporated and can not be immediately captured to serve new uses, and industrial uses in which the water is incorporated into a production. For the most part, industrial and indoor household uses are non-consumptive, however, in almost all cases the quality of the water is degraded so that some form of treatment is required before it is available for further use.
The availability of water for withdrawal use is determined, at least in part, by the proportion of the supply allocated to instream uses. While instream uses do not render water unavailable for additional use, where water supplies are scarce, instream and withdrawal uses tend to compete. The importance of water in supporting the instream uses to maintain biodiversity and environmental quality is explored in the next chapter.
Regional Determinants of Water Use
While the overarching factors just discussed explain much of the magnitude of water use, both supply and demand for water are further determined by location-specific variables. The availability of supplies depends, for example, on the costs of developing and transporting the water and of any treatment needed to ensure that the water is of suitable quality for the use. Similarly, the demand for water depends on the water-intensity of local and regional economies and—where domestic use and agricultural irrigation are important—the local climate.
There are virtually no studies of the determinants of water use in the study area. The vast majority of studies on determinants of water use in semiarid environments have been done of the western United States (see, for example, Howe and Linaweaver, 1967; Bruvold, 1988). A review of
these studies suggests variables that may be important in estimating the demand for water in the study area.
Municipal and Industrial Sectors
The amount of water withdrawn and consumed by the municipal sector is in large measure a function of the population size. The need for water to supply people's basic needs for drinking, cooking, and sanitation is proportional to the number of people and their standard of living. Varying quantities of water may be used for other household purposes beyond these fundamental needs, and these quantities will also be related to the number of people, though less directly so. Changes in technology or behavior that alter levels of water withdrawn and consumed may have significant impacts on the total levels used and the proportion returned as waste. It would be useful to investigate the effects of drought on water use; reductions on outdoor uses of water and economizing on indoor uses reduced total domestic water use by 25 percent in California during the drought of 1987-1993.
Domestic household water use is also importantly influenced by the number of persons in the household. Interestingly, data have been reported that show declining per capita use rates as the number of persons living in the household increases (Howe and Linaweaver, 1967; Bruvold, 1988). Household water-using technology, such as low-flow toilets, may also be an important determinant of per capita domestic water use, as are household appliances such as clothes- and dishwashers. A working water meter and accurate metering and reporting of water use have also been shown to be important determinants of water-using behavior in the household. Outdoor use of water may account for a significant percentage of total household water use, though irrigated landscaping is far less prevalent in the study area than it is in the semiarid western United States. Finally, household income and the price of water have also been shown to be important determinants of water use (Howe and Linaweaver, 1967; Bruvold, 1988). It is generally recognized that adoption of water-saving technology and drought-resistant landscaping, programs of education, and changes in prices and pricing systems can all have significant impacts on domestic water consumption. These determinants should be considered in developing any water plans for the region.
Determinants of industrial water use and return vary from industry to industry. They are importantly influenced by the technology employed. There is clear evidence that stringent standards or regulations governing the quality of discharge waters can lead to intensified recycling of industrial water, with significant reductions in total water used as well as a reduction in the quantity of wastewater discharged. Determinants of
commercial and public uses are less well studied and understood. Again, a more complete picture could be obtained by checking the effects of droughts on the use of water in these sectors. Public uses are importantly influenced by the area of open space such as parks. While the patterns of municipal water use in the study area may not be closely similar to those of the western United States, the U.S. studies are likely to provide useful information in examining determinants of municipal and industrial water use in the study area.
The determinants of agricultural water use are generally quite well known. The greatest factor influencing evapotranspiration is solar radiation. However, different crops may have different requirements for evapotranspiration, so that consumptive water use in the agricultural sector also depends on crop type. Evapotranspiration is also influenced by other climatic variables, including temperature, humidity, and wind speed. The same crop has different evapotranspirative requirements in different climatic zones. In addition, different irrigation methods such as drip, sprinkler, and different techniques of gravity irrigation, and the employment of closed-conduit irrigation technology may also reduce the quantities of water consumed at the farm level for the same crop production. The price of irrigation water has been shown to be an important water use determinant, but the impact appears to be largely on the type of crop selected rather than the amount of water applied (Green et al., 1996). Other things being equal, high-valued crops—particularly fruit, nut, and vegetable crops—tend to be grown in areas where irrigation water prices are high. There is also evidence that high water prices result in investment in technology and management regimes that reduce water losses at the farm level.
Reductions in use at the farm level may not always translate into reductions in aggregate water use. Frequently, changes in irrigation technology or management regimes result in reductions of deep percolation and runoff. In most instances, water that deep percolates from irrigated areas constitutes ground-water recharge, and water that runs off from fields is a source of supply for someone else. As a consequence, agricultural water conservation programs need to be carefully tailored to ensure they result in true water savings and not simply savings at the farm level that reduce someone else's supply (Council for Agricultural Science and Technology, 1988).
There is less information on the determinants of both municipal and agricultural water use in the study area than is desirable. The development of water management plans and the delineation of various options
and levels of balanced water supply and demand will ultimately require a better understanding of both the patterns of water use and the determinants of those patterns.
- A review of studies undertaken elsewhere in the world should be carried out to identify water use patterns and the determinants of those patterns. Such a review should be very helpful in structuring similar studies for the study area.
- The committee recommends that such studies of water-use patterns and their determinants be undertaken for the study area as soon as feasible as part of the regionwide water planning effort.
Criteria for Selecting among Water Use Management Options
As the populations and economies of the study area change, different water management options will need to be developed and assessed. Levels of water use can be affected both by managing variables that affect demand and by employing new water supply technology—undertaking new development, where warranted, or developing new water supply regimes. Specific options to manage demand and augment supplies in the region are considered in Chapter 5 of this report. The particular combination of supply and demand management measures selected will significantly determine the region's patterns of water use. As we have described above, these variables make accurate, precise predictions and projections impossible. Therefore, instead of basing evaluations of plans on necessarily inaccurate projects or scenarios, the committee has identified and applied the following criteria to make a critical assessment of the various options presented in this report. In fact, these criteria are essential in assessing any water use management option, especially in a water-scarce region like the study area.
What is the likely magnitude of impact on available water supply? Other things being equal, options that have relatively large positive impacts on available water supply, whether individually or in aggregate, will be more desirable than those that have more modest effects. In many circumstances, programs of demand management that induce economizing on water use may have very significant impacts on the available supply of water. Options to enlarge the available supply of water are clearly not restricted to supply augmentation or development projects.
Is the option technically feasible? Supply augmentation and demand
- management options must be technically feasible. In evaluating options, care should be taken to assess whether the option is currently technically feasible, and, if not, whether it could be made so with a modest additional investment in research and development.
What is the environmental impact of the option? Will the option reduce or increase the quantities or qualities of other water supply sources? Does the option have adverse environmental impacts? Beneficial environmental impacts? What is the impact of the option on aquatic and terrestrial habitats? Will the option lead to losses of unique plant and animal communities or particularly valuable species? (See Chapter 4 for an extended discussion of these general issues.)
Is the option economically feasible and fair? What factors affect the economic feasibility of the option? Has the option proved economically feasible elsewhere? Will local circumstances have a significant impact on either the costs or the benefits? In assessing economic feasibility, all costsæincluding the costs of technical external diseconomies—must be considered. Additionally, all costs and benefits must be reported together with appropriate specific information about who will bear the costs and who will receive the benefits of any options.
What are the implications for intergenerational equity? For purposes of analysis, the notion of intergenerational equity can be defined in terms of three principles. The principle of future options requires that actions taken now do not unduly restrict the opportunities for future generations to satisfy their own needs and advance their own welfare. The principle of conservation of quality requires that the quality of the environment be fully maintained for future generations. The principle of access requires that each generation be provided with access to the legacy of the past, and that this access be conserved for future generations. Each option should be assessed in terms of how well it adheres to these three principles of equity. The concept of sustainability as expressed in intergenerational equity, is variously defined in reports by scientific and public-policy organizations. It always requires some assumption—implicit or explicit—as to time horizon, the elements of environment to be maintained, and the societal standards for the access to be conserved for a specified population. (Some representative definitions are listed in the bibliography.)
Berkoff, J. 1994. A Strategy for Managing Water in the Middle East and North Africa. Washington, D.C: The World Bank. Pp. 72.
Bruvold, W. H. 1988. Municipal Water Conservation. Contribution # 197. University of California Water Resources Center, Riverside.
California Department of Water Resources. 1994. California Water Plan Update. Bulletin 160-93. Sacramento, California.
CES Consulting Engineers and GTZ. 1996. Middle East Regional Study on Water Supply and Demand Development, Phase I, Regional Overview. Sponsored by the Government of the Federal Republic of Germany for the Multilateral Working Group on Water Resources. Eschborn, Germany: Association for Technical Cooperation (GTZ).
Council for Agriculture. 1988. Effective Use of Water for Irrigated Agriculture. Task Force Report No. 113. Council for Agricultural Science and Technology, Ames, Iowa.
Green, G., D. Sunding, D. Zilberman, D. Parker, C. Trotter, and S. Collup. 1996. How does water price affect irrigation technology adoption? California Agriculture 50(2)March/April:36-40.
Howe, C. W., and F. P. Linaweaver, Jr. 1967. The impact of price on residential water demand and its relation to system design and price structure. Water Resources Research 3(1):13-32.
National Research Council (NRC). 1987. River and Dam Management: A Review of the Bureau of Reclamation's Glen Canyon Environmental Studies. Washington, D.C.: National Academy Press. 152 pp.
National Research Council (NRC). 1989. Irrigation-Induced Water Quality Problems. Washington, D.C.: National Academy Press. 157 pp.
National Research Council (NRC). 1996. River Resource Management in the Grand Canyon. Washington, D.C.: National Academy Press. 226 pp.
United Nations (UN). 1996. Comprehensive Assessment of the Freshwater Resources of the World. The United Nations, New York, NY.
Vaux, H. J., Jr. 1991. California's water resources. Pp. 69-96 in Global Climate Change and California: Potential Impacts and Responses, J. B. Knox and Ann Foley Scheuring, eds. Berkeley, CA: University of California Press.