Of all our available resources, water is the most precious. Public water supply, aquatic habitats, energy generation, agriculture, industrial, commercial uses and recreation –all depend on water. The hydrologic cycle or the water cycle in nature describes the continuous movement of water on, above and below the surface of earth from one reservoir to another such as from rivers to oceans or from oceans to atmosphere and then atmospheric circulation moves water by rain, snow etc through the process of infiltration and surface runoff in rivers and streams and in ground. Most of the earth’s water is in ocean and most of the fresh water is stored as ice or below ground in aquifers, thus comparatively little fresh water is available for human use on a global scale, e.g., only 0.77 % of all earth’s water is available as fresh ground water or surface water and only .008 percent is available in lakes, rivers and wet lands (Shiklomanove 1993).Thus water conservation is desirable in any water use sector by considering the limited availability of fresh water on a global scale. The rivers health and the availability of fresh water are very much interconnected.
The Nation’s network of rivers, lakes and streams originates from a range of small invisible streams and wetlands, yet these head water affect the health and efficiency of downstream water. The natural processes that occur in such head water benefit human by flood mitigation, maintaining quality and quantity of water, recycling nutrients and providing habitats to plants and animals. Therefore the health and productivity of rivers and lakes depend upon the intact streams and wetlands and changes in its vicinity, no matter in land use pattern or in vegetation cover can impair its natural functions and can scour its channels and such altered channels cause more frequent and bigger flood. These channels are also less effective in groundwater recharge, trapping sediments and recycling nutrients. As a result the downstream rivers and lakes water quality, flow and diverse aquatic life is compromised and costly dredging is needed to clean the channels and thus increase water filtration cost for municipalities and community .Therefore to sustain the health of our nation’s water, the hydrological, biological and geological characteristics of these wetlands and streams require protection on priority basis.
Healthy rivers and streams support a complete ecosystem, diversity of fish, wildlife and provide recreation facilities to million people in the country. The rivers natural flow, seasonality, volume, duration, regularity, rise and fall over time operate many ecological processes and physical conditions and are natural tools in providing clean water, flood protection, ground water recharge, wild life, healthy riparian forest and recreation. However traditional on stream water storage reservoirs and dams can cause irreversible damage by adversely affecting the rivers and streams health and their associated environment, recreation and economic value. The river imbalanced flow also harms fisheries and natural wonders.
In addition, water supply reservoirs and high withdrawal from surface or ground water have significant negative environmental and economic impacts and cannot address the root cause of the problem and the use of our limited supply more wisely.
Environmental Impacts
Though reservoirs and dams are often the first choice of the water authorities to seek demand meeting from a quick fix of reservoirs and dams water but ignores the devastating impacts of reservoirs and withdrawals on its impounded area and upstream and downstream reaches which , is the primary cause of ecological impairment in river and stream ecosystem by disrupting the habitats of many migratory fish and associated species that cannot bypass the barriers to reach habitats and spawning grounds in upstream reaches.
Also the physical, chemical and biological health of down stream reaches is affected due to altered hydrology which disintegrates physical stability and sediments transport dynamics of the area. Similarly it affect the water quality, eliminate natural biodiversity, change water and food transport downstream, increase temperature, decrease dissolved oxygen and induce changes in the life cycle of aquatic species.
Furthermore, narrower range of flow disconnect rivers and flood streams from flood plains, reducing hydration of riparian areas and the volume of water downstream. Also reservoir not only disrupts the water cycle of watersheds and rivers basin but also increase water loss due to evaporation.
Many aquifers throughout the country are under stress due to increased pumping from tube wells or making new wells with no recharge results, in diminished water quality, dry well, salt water intrusion, land subsidence and reduced stream flow in rivers where there is a connection between ground water and surface water and high withdrawal can cause low flow or no flow conditions in the surface water. Therefore the groundwater management Act enforcement is needed at urgent basis.
Economic impacts:
Development of new reservoir, treatment and distribution infrastructure can be very expensive in terms of land acquisition, debit servicing, manpower, transport, machinery and energy comparing to water conservation and efficiency measures. According to the Georgia Environmental Protection Division 2008 papers, dams and reservoirs can cost $4000 per 1 gallon of capacity where as water saving and efficiency cost $ 0.46 to $250 per gallon saved or new capacity. Also developing a new reservoir should include the cost of environmental impact of the ecology and mitigation of wet lands and streams and that make it too expensive for agriculture and municipalities use.
Reservoirs are costly to build and cannot be easily expanded to the growing demand. Often it is constructed upfront which increases its financial risk by disturbing the geology and hydrology of the area that create over flow or under flow situations. Evaporation losses and sedimentation compounds further its diminishing value and its remediation is time consuming and costly. Similarly the massive pipe line and pumping energy is costly to ensure the supply of water.
Equally prohibitive to system expansion is the population density near the upstate water shed and due to incremental development pressure close to and with in the watershed localities, the water quality is adversely affected. Also reservoir needs operation and maintenance at regular basis and takes years to build.