2.12 Concluding remarks

2.12.1 Remarks on the review study

This study was initiated to review the problems and constraints of waterresources development and management in the arid zone, including nonconventional water-resources development alternatives as summarized below.

In the Middle East the potential for the development of renewable water resources is limited, owing to the scarce rainfall with very high potential evaporation.

MULTINATIONAL RIVER DEVELOPMENT. There are two major water resources issues in the world's large river developments in the arid region: the quantity issue in inter-state water allocation, and the quality issue of salinity problems. Various and serious salinity problems have been major issues in the basin management of large rivers since the mid-twentieth century, including the Indus River in South-West Asia, the Tigris, Euphrates, and Jordan Rivers in the Middle East, the Nile River in North Africa, and the Colorado River in south-western Arizona in the United States of America.

RIPARIAN ISSUES. Many countries of the Middle East, except for those in the Arabian peninsula and Libya, depend on three major river basins: the Tigris-Euphrates, the Nile, and the Jordan and Litani. Given that these rivers do not respect national boundaries and that those states located upstream have obvious advantages both political and economic over those downstream, the potential for conflict over water is great.

Salinity control in the rivers is needed to protect the quality of the environment in the river system and to maximize the quantity of water available for downstream irrigation or other water supply. Reverse osmosis desalination of brackish water will be a key technique for sustainable basin management in the twenty-first century.

Owing to increasing demand and limited recharge potential for conventional renewable fresh groundwater resources, many states in the Middle East have already over-exploited the sustainable yield. Careful groundwater management will be essential to sustain further development.

NON-RENEWABLE GROUNDWATER RESOURCES DEVELOPMENT. A vast amount of the non-renewable or fossil groundwater is trapped in the Palaeozoic to Mesozoic-Neogene (Nubian) sandstones that underlie wide areas of the Arabian peninsula and the eastern Sahara desert in Saudi Arabia, Jordan, Egypt, and Libya. The dominance and importance of this resource will be paramount in water-resource planning and strategy in many countries, especially Egypt, Libya, Saudi Arabia, Kuwait, Qatar, and Bahrain.

Non-renewable or fossil groundwater resources should be saved as a strategic reserve except for emergency or short-term use.

DESALINATION OF SEAWATER. Desalination of seawater is likely to be required more and more to make up deficiencies in supplies of water from other sources.

The prevailing multi-stage flash desalination will be replaced by processes requiring lower capital and lower operating costs such as low-pressure types of reverse osmosis. The role of the ocean, which contains the largest water reserves on earth, will be important for sustaining water-resources development in the twenty-first century.

SOLAR-HYDRO DEVELOPMENT. The Mediterranean-Dead Sea canal scheme should now be reassessed in the joint development.

Groundwater-hydro and solar-hydro are likely to be a strategic priority to save fossil energy and the global environment with economic feasibility.

Strategic priority should be given to reverse-osmosis desalination, including research into hydro-powered co-generating applications, which will result in developing more low-energy-dependent membranes with significant cost reductions.

Water conservation and sustainable water-resources management will be key measures to sustain the economic development of the arid states, and may even include the cutting of part of the national water supply from non-renewable sources. The conservation approach has to be performed in parallel with developing non-conventional water resources, taking into account new developments in the technology of desalination, wastewater treatment, and water-saving techniques.

Water-resources planning studies in arid regions, especially in developing countries in the Middle East, must consider the following strategic development alternatives:

>> water conservation, including the diversion of existing water sys tems from one use to another;

>> maintaining fossil or non-renewable groundwater resources at strategic reserves, with the exception of emergency or short-time use for specified purposes;

>> non-conventional water-resources development, including desalination and reuse of treated sewage;

>> inter-state water transfer or importation.

Priority will have to be given to domestic water-resources development, management, and conservation, including non-conventional measures, rather than reliance on importation from outside countries. Inter-state riparian issues of water allocation have to be resolved in a context of basin master planning.

Water-resources planning, especially master planning for inter-state basin development, must include recognition of techno-political issues. It is suggested that techno-political feasibility should be evaluated and resolved in the context of a master plan. For further details on techno-politics see sections 5.5 and 5.6.

2.12.2 Marginal waters as potential non-conventional water resources

After reviewing the problems and constraints of water-resources development and management, the study focuses on marginal waters as non-conventional water resources in arid to semi-arid regions. Almost all the fresh and renewable natural water resources in the rivers, lakes, and aquifers in the arid zone, which are referred to as "conventional" water or "traditional" water, have already been exploited or will be fully developed by the end of the twentieth century. Furthermore, all major rivers in the arid zone have already been seriously contaminated by accumulated salt in the return flow from irrigated land, and severe water shortages are being felt in many urban centres as populations continue to grow. After completing the exploitation of renewable water resources, we may have only limited options to sustain water development, including:

>> making more efficient use of available water supplies,

>> diverting water from one use to another,

>> developing marginal waters as non-conventional water resources, >> importing fresh water from neighbouring countries,

>> importing food commodities as a proxy for water (e.g., 1 ton of wheat = 1,200 tons of water).

Table 2.13 Conventional and oon-conventional water resources categorized by hydrological system

Marginal waters may occur in any category of hydrological system- atmospheric, surface water, groundwater, and ocean systems-as shown in table 2.13.

Potential applications in the atmospheric system include cloud seeding, or artificial rain, which is possible in some very limited areas in high mountain ranges such as the Anti-Lebanon where winter precipitation is 1,000 mm or more (Kelly 1974).

Marginal waters in the surface-water system such as waste water and irrigation return flow are major sources of water reclamation. The probability that the results will be economically feasible is high, but this will depend on advanced waste-water-treatment technologies to be applied in the twenty-first century. The increasing demand for water supply, especially in urban centres, may create an increasing potential for water reclamation. Such water will be used mainly for secondary purposes such as garden/landscape irrigation and irrigation of specific crops (Wesner and Herndon 1990).

Marginal waters in the groundwater system include non-renewable or fossil groundwater, brackish groundwater, and artificial recharge from surface waters and treated sewage effluents. Artificially recharged groundwater is a marginal water in the arid zone, and may be involved in conjunctive surface-groundwater uses.

Brackish groundwaters with higher salinities such as 2,000-10,000 mg of TDS per litre have not been developed except for use in blending with fresh surface water or distilled water from desalination plants. In the arid zone, however, the reserve potential of brackish groundwaters in deep aquifers is great as compared with fresh groundwaters in shallow aquifer systems near the recharging area. RO desalination of brackish water has been only marginally feasible in the 1980s, but it is becoming more cost-effective and is regarded as an energy-conserving measure for developing water resources in the arid region. It will be a key technology for non-conventional waterresources development in the arid countries.

An extremely slight amount of seawater is being used for water supply through desalination plants. Seawater desalination has been practiced mainly in oil-rich desert countries of the Arabian Gulf where conventional renewable water resources are scarce. In the 1970s, largescale seawater desalination projects were considered that would be both technically and economically feasible as water-supply alternatives today (Buras and Darr 1979). Cost constraints remain, but there is no doubt that seawater will be the ultimate water resource in the arid zone, coupled with food imports as a proxy for water. Current innovative research in desalination technology, especially on reverse osmosis membranes, is changing the cost environment by reducing both capital costs and operation and maintenance costs over the conventional MSF process which has been used so far almost exclusively in the Middle East states (see Appendix A).

Potential marginal waters as non-conventional water resources thus comprise primarily brackish waters, seawater, and reclaimed urban waste waters. These are the keys to developing water resources in the twenty-first century, taking into account that almost all the arid states in the Middle East are completing or depleting the development of their conventional water resources.

The cost and viability of technology are the key factors in the development of non-conventional water resources. Desalination of brackish water can provide a relatively reliable source of water for costs ranging from US$0.25 to US$1.00 per m³ in the mid-1980s and is becoming even more cost effective by the development of low-pressure (low energy) types of RO membranes. Seawater desalination and water transport by tanker may provide water for costs of US$1.25 to US$8.00 per m³ (DTCD 1985). The reuse of waste water gives a lower quality water at the cheapest price, while weather modification has the potential to provide a low-cost but relatively unreliable source of water and technology for it.

Table 2.14 Hydro-potential and thermal-energy applications in water-resource systems

2.12.3 Applications in hydro-power and co-generation developments

The use of marginal waters should not be limited to exploiting water for municipal and industrial water supply and irrigation. After the Iraqi invasion of Kuwait in August 1990, worldwide attention was focused on the energy crisis and the need to minimize or reduce world energy consumption to sustain both human life and the global environment. The application of non-conventional water resources development with cogeneration of thermal and hydro-power energy conversion may be used (1) to reduce capital investments, (2) to cut power-supply costs, and (3) to contribute to saving precious energy. Table 2.14 lists possible measures to develop hydro-potential and thermal energy in a waterresources system. Co-generation applications of seawater pumpedstorage schemes with hydro-powered RO desalination are discussed in section 5.6.

2.12.4 integration of marginal waters in national water master plans

This study has aimed to identify techno-political development alternatives for marginal waters as non-conventional water resources. These development alternatives are likely to be integrated in nationwide and/or multinational-level water master plans.

The study is focused on the development and management of saline water resources, including desalination by reverse osmosis with appli cations of co-generation alternatives, and suggests that marginal waters produced by RO desalination will play an increasingly important role in the twenty-first century's water-resources planning in the arid countries in the Middle East. It is not intended, however, to suggest that the RO process will necessarily be the only or best one in the future, taking into account potential progress in research on and the development of other new technologies.