Availability of water in a given soil environment is a critical factor and is related to erosion, siltation, loss of plant cover and productivity. In India floods bring considerable damage resulting in loss of life and property each year. Due to floods, the plains have become silted with mud and sand that affect the cultivable lands.
The National Commission on Floods has calculated that the land areas prone to floods have doubled from 20 million hectares in 1971 to 40 million hectares in 1980. The worst flood suffering states are Bihar, Assam, Orissa, U.R and West Bengal.
The management of rainfall and resultant run-off is very important and found to depend on watersheds. A watershed is an area bounded by the divide line of water.
Thus it may be a drainage basin or stream. The Himalayas are one of the most vital watersheds in the world. These watersheds are threatened by deforestation and other ecological malpractices and have resulted in depletion of water resources. Thus for watershed management following measures to be adopted
1. Soil and land use survey.
2. Soil conservation in catchment of River Valley Projects and flood prone areas.
3. Afforestation, Social Forestry Programs and Drought Prone Development Programs.
4. Desert development.
5. Control of shifting cultivation.
Watershed management practices: In the Fifth Five Year Plan, watershed management approach was included with a number of programs and a national policy was developed. The practices of conservation and development of land and water are taken up with respect to their suitability for peoples benefit as well as sustainability. The various methods taken up for management include the following:
(i) Water harvesting: Proper storage of water is done with provision for use in dry seasons in low rainfall areas. It also helps in moderation of floods.
(ii) Afforestation and agro forestry: In watershed development, afforestation and crop plantation play a very important role. They help to prevent soil erosion and retention of moisture. In high rainfall areas woody trees are grown in between crops to substantially reduce the run-off and loss of fertile soil.
In Dehradun, trees of Eucalyptus and Leucaena and grasses like Chrysopogon are grown along with maize or wheat to achieve the above objectives. Woody trees grown successfully in such agro forestry programs include Dalbergia sissoo (Sheesham), Jectona grandis (Teak) and Acacia nilotica (Keekar) which has been used in watershed areas of river Yamuna.
(iii) Mechanical measures for reducing soil erosion and runoff losses: Several mechanical measures like terracing, bunding, bench terracing, till farming, contour cropping, strip cropping etc. are used to minimize run-off and soil erosion particularly on the slopes of watersheds.
(iv) Scientific mining and quarrying: Due to improper mining, the hills lose stability and get disturbed resulting in landslides, rapid erosion etc. Contour trenching at an interval of 1 meter on overburden dump, planting some soil binding plants like Ipomoea and Vitex and draining of water courses in the mined areas are recommended for minimizing the destructive effects of mining in watershed areas.
(v) Public participation: People’s involvement including the farmers and tribal is the key to the success of any watershed management programs particularly the soil and water conservation.
The communities are to be motivated for protecting a freshly planted areas and maintaining a water harvesting structure implemented by the government or some external agency (NGO) independently or by involving the people in campaigning and its benefits or sometimes paying certain incentives to them can help in effective people’s participation.