ALL five dams, Bhasha, Munda, Kalabagh, Akori and Kurrum Tangi, would be built by 2016. The building of water reservoirs in the upstream reaches of a river will impact the volume of water flowing in the downstream areas.

To avoid this problem, there are a number of alternatives which can be used quite often in combinations as substitutes of dams. Water diversions can be achieved by alternatives like infiltration galleries. These are structures which are used for diverting water.

There are two types of infiltration galleries: vertical wells and horizontal infiltration galleries. Through gravity flow or pumping, water is drawn from the river’s gravel substrate through perforated pipes.

Vertical wells draw water through perforated pipes, which are placed vertically into the stream. The water table is maintained by the surface flow of water in the stream. Location of vertical wells is dependent on river conditions. They can be located near or away from the river.

Horizontal infiltration gallery concept is simple and convenient. The infiltration gallery structure typically involves locating perforated pipes in the riverbed and, these pipes discharge to a sump. Water seeps in the perforated pipes and flows to sump. Water collected in sump flows by gravity (or is pumped, in some cases) to a point where it is used or stored.

Location of perforated pipes and its diameter is governed by the factors like rate of diversion of water, type of gravel at the site, the depth to which bed scouring is likely to occur during high flows in the river, and the size of river itself.

Infiltration galleries may face problems if armoured gravels are on the riverbed as that would reflect low percolation rates. Fine-grained soils such as the clay, silt and sand would cause logging. Absence of gravel substrate may prevent the placement of perforated pipes at depths sufficient to protect them from scouring.

Seasonal dams are temporary and relatively small structures that can be erected for water diversion. They raise the river water level allowing water to be diverted through a channel or pipe. Flashboard and inflatable dams are the common types of seasonal dams. Despite their smaller size, seasonal dams can affect rivers negatively by increasing water temperatures, harbouring predator species, reducing downstream water flows and associated aquatic life, inducing erosion of the bed and banks of rivers, causing fluctuations in upstream water levels, and impacting biota and aquatic vegetation. The magnitude of negative impacts is small and easily manageable.

Agriculture is the largest user of water. Irrigation-purpose water supply dams are common worldwide. In this case, alternative diversions need to be coupled with irrigation practices. Rational irrigation practices which can even obviate the need for a dam, include efficient water distribution (land levelling), achieving better soil moisture retention (furrow dykes to prevent runoff), dry-land farming (coordinating seeding to ideal soil moisture, choosing crops more suited to water-deficit conditions and fallowing), land retirement (temporary suspending farming on a particular unit of land in exchange for financial incentives) and, land chiselling (allowing land to absorb water more efficiently).

Management strategies help in ensuring efficient water delivery. The strategy components are scheduling irrigation, determining soil moisture, measuring rainfall and, checking pumping efficiency.

It requires the education of irrigation staff through agriculture extension services. Use of drip irrigation or micro-sprinklers, solid set systems, and constructing a tail-water recovery system has the potential to further improve the water efficiency.

Alternate arrangement for use of water attempts to seek out sustainable management and can provide additional water for use. Rain is the major source of water. Concrete and other impervious surfaces are increasing in peri-urban areas. This prevents natural infiltration and interferes with hydrologic cycle of nature. Aging pipes and infrastructure give rise to water loss. In Karachi, the local water agency loses 33 per cent of water supplied to city due to pipe leakage and water vandalism.

Groundwater is a major water resource in Sindh, but its potential use is reducing due to pollution. Sustainable use of groundwater can reduce reliance on surface water supplies and dams.

Rainwater harvesting is an old trusted practice of collecting rainwater from rooftops and storing it in drums. Water can be used in lawns, or for drinking after passing it through filters. It reduces storm-water runoff; prevents flooding, erosion and pollution of surface water bodies.

Recycling and re-use of water has the potential of entailing large savings and can decrease the amount of freshwater required. Recycled water can be used for irrigation and in industries. Water pricing is a useful way of conserving water. Seawater desalination is an attractive alternative of avoiding use of freshwater. There are many technologies of separating salt from water but the two most common are reverse osmosis and thermal distillation.

There is no separate department for freshwater management in Sindh. The set-up of Sindh Freshwater Management Department is suggested with staff qualified in water engineering. The Sindh government should take the matter seriously.

The case of Aral Sea should be an eye-opener. Decline of the Aral Sea started in the 1960s as increasing amounts of water were diverted from the Amu Darya and Syr Darya mainly for irrigation. Between 1960 and 1996 the surface area of the sea declined by some 50 per cent (from 67,000 square km to 30,000 square km) and, the sea level dropped by 16 meters.

The desiccation of the Aral Sea and the damage to the river deltas resulted in serious economic, social and environmental consequences such as (i) elimination of fish production in the delta as well as hay production along streams, lakes and wetlands; (ii) extremely high levels of salinity and pollution; (iii) dust and salt storms occur often and climatic changes take place around the sea; (iv) non-availability of adequate and safe drinking water supplies; (v) increase in human health problems resulting in reduced life expectancies in the areas near the sea; (vii) elimination of tens of thousands of jobs in fishing, agriculture and service sectors, and; (viii) degradation of agricultural lands, soil, surface waters and groundwater and, wetlands.