Limited role of Watershed Development (WSD) and rain-water harvesting in ensuring water security

A land mass, where precipitation received is passed through different phases of the hydrohgical cycle, viz: partially stored /abstracted for use by human / ecosystems, evaporated, transpired, infiltrated, and ultimately naturally drained out through a common outlet; is known as a watershed (WS). For a river, its entire catchment area is its WS. Each stream from 7^st order, down to each tributary (the smallest to the largest) has a distinct WS of its own. The categories for a WS therefore comprise: river basin, sub-basin, WS, sub-WS (SWS), micro WS (MWS). The first two categories are normally excluded from the popular perception of a WS.

Development of a WS connotes soil and water conservation measures which include: contour bunds, terracing, gully plugs, vegetative barriers, appropriate farming measures including ploughing and tilling, according to the soil morphology. The measures make maximum quantum of water to infiltrate into the ground, augmenting soil moisture and charging underground aquifers, in tune with properties of the sub-strata and land morphology; reduce soil erosion reducing the surface run-off. They promote interflow causing a better time-distributed flow in downstream, generating more biomass (grasses, crops, forests) than before. The measures thus conserve and augment moisture in soils/sub-soil / biomass. It otherwise flows as surface runoff through the mouth of the WS, unless captured and stored in a surface storage. Small storages like farm ponds, check dams, village tanks, percolation tanks and minor irrigation tanks also are considered as interventions in the WSD. Although major multipurpose development schemes comprising dams and dependent systems though strictly are also WSD measures, are not popularly so considered.

RWH really is a sub-set of WSD. Like a harvest of crops or biomass from a piece of land, water harvesting connotes catching rain, where it precipitates and utilizing it like a harvest. Local catch and use are the keys to RWH. Obviously, it includes the smaller interventions out of the whole lot described above. WSD collects water over a larger area, stores it and then allows its use.

Difficulties related to submergence of useful land and forests, besides displacement of residents, grew with the scale of Water Resources Development (WRD). During the last two decades in particular, the WSD at micro level and RWH therefore came to be advocated with a promise of a better option. The interventions claim to address difficulties of small land holders, economically weaker farmers, who are totally dependent upon rainfall incidence, its variation, and resultant subsistence farming. More importantly, traditional wisdom was considered to be fully utilized in the WSD-RWH phenomena. No doubt they need to be valued but evaluated also. After all they were developed when the societies dependent on them were small. The problems were on a small scale altogether. The traditional methods therefore have to be deployed with abundant caution. Claims made have to be tested against the present day requirements. Those who oppose larger scale of WRD advocate them for their own reasons. Gradually, the concept has gathered hype and is now touted as a panacea for all the perceived so called 'ills' of the water sector.

The paper brings out, the weaknesses of such advocacy, describes the limitations of the WSD-RWH concepts, the practices and highlights the situations where these succeed. It depicts the role of WSD-WRH in the long term water security. Finally, it makes out a case for integrated use of every option for infrastructure development in a discrete combination for intra and inter-basin river WRD for a country.