Different types of activities can be implemented for watershed area development, which instead is development of the area.
This includes construction of different structures for soil and water conservation. Both cultivable as well as uncultivable lands are covered in it.
It is desirable to give a detailed technical knowledge about such structures here so that development workers can make sustainable development in any geographical region by following them.
They are as follows:
Leveling and Contour Bunding:
So far, big pakka structures have been constructed for soil and water conservation but they were not suitable from economic and environmental point of view. They could also not associate a large number of people and give employment to them. Hence, for soil and water conservation, trenches and earthen check dams in uncultivable lands, and leveling of land in cultivable lands along with contour bunding were started in modern forms.
Rain water was absorbed in the field itself by contour bunding so that the water did not flow uncontrolled to cause soil erosion nor did it develop gullies and spoil the soil. Height of these bunds was proposed to be 40 cms to 60 cms and for stability of these bunds during rain, local grasses were also planted over them.
In desert regions like Rajasthan, though the problem of water How is not there due to scanty rainfall, but severe problem of soil erosion is noticed due to dryness and fast flow of air. In these areas, ‘Kanabundi’ is done for soil conservation.
In ‘Kanabandi’, a row of dry shrubs and grasses are erected against the wind direction, so that blowing away of earth is prevented. Dry shrubs convert into organic manure after decay, which both contribute to better production, and reduces formation of sand dunes. For stabilization of fine sand dunes, mulching of dry shrubs is also done in desert areas.
Vegetative Filter Strip:
An irregular and continuously changing vegetative filter strip is prepared by planting local shrubs. Its plantation is done in such a way that it develops in shape of a net and the flowing water passes through it after being filtered. This technique is known as vegetative filter strip. Because of filtering of water through the strip, not only does the force of water flow reduces but silt is also prevented from going farther due to filtering.
Hence, soil erosion is controlled. Moreover, availability of biomass also increases in the form of vegetative filter strip in the watershed area. Such type of structure is developed mainly at places where soil erosion is faster due to changing flow of water and water does not stop flowing. After development of a vegetative filter strip, flowing water goes under the ground slowly and increases the groundwater. This is suitable for cultivable as well as un-cultivable lands.
Contour Vegetative Hedge:
For establishing Contour Vegetative Hedge, vegetative hedge of local species is planted according to the structure and slope of the land. After planting it in the lower boundary of the field, hedges are erected in the route of flowing water so that soil flowing with water may stop and water is filtered so that it flows gradually. This controls soil erosion and also prevents soil decay. It also increases availability of biomass in the area. Roots of trees planted in the contour vegetative hedge hold fast the soil and there is no investment except for the normal cost of plants.
Generally, contour vegetative hedge is planted on lands having normal to medium slope. These hedges are planted by the sides of narrow furrow, trench or bund. They can also be laid by the sides of streams in flood affected areas.
In the present context of watershed development, some of the following facts are worthy of consideration:
1. Government of India has recommended plantation of ‘Vetiver’ grass under the Watershed Area Rainfed Agricultural System Approach (WARASA), as the best available conservation vegetation.
2. In Rajasthan, vegetative species like Ber (Zizyphus), Mehandi, Moonj, Dhaman grass, Khas, Hemta, Lemon grass and other local brands of vegetation can be used.
Gully control is an important conservative measure in uncultivable land reform programmes. It controls soil erosion from being caused in watershed areas. The upper layer of soil is destroyed by gully erosion and the levelled ground becomes a wide and deep valley after that.
Soil erosion can be controlled by constructing check dams and developing vegetative covers. The form of gully erosion depends on the hydrological condition, quantity of silt, and requirement of vegetation by soils and people. Gully erosion mainly depends on necessity of vegetation by the structure of the check dam and gully erosion can be mainly controlled by check dam structures.
Check dams are of two types:
(1) Pervious Check Dam
(2) Impervious Check Dam.
Classification of both these types depends on the structure of flow of water from any tank or gap. Check dam is constructed on the upper parts of a river. The number of check dams that may be constructed over a river would depend on the flow of water, slope and force of the flow. This number may vary from one to one hundred. This whole system can be constructed with the participation of the local people.
Pervious Check Dam:
The main objective of constructing such a check dam is to filter the flow of river water after controlling the eroding power of water so that silt deposits in it, and the water moves ahead after being filtered. Its construction is done with logs of wood and pieces of rocks. Water remains stored for local use in it, but it is constructed for some future object. Its construction can also be done by trees of thick wood, loose stones, and fences.
Impervious Check Dam:
This dam is constructed on natural ground parts or concrete, and stone is used for strong cover. It is usually constructed in loamy soil or barren land where gullies are formed of shallow and loose soil. The objective of construction of impervious check dams is to use water after its storage as well as to check soil erosion since water does not pass through these structures.
Conservation measures of check dams have following advantages:
i. Force of flowing water is reduced by check dams.
ii. Power of eroding capacity of water is reduced by them.
iii. There is improvement in moisture condition of soil also.
iv. There is reduction in severity of floods.
v. There is storage of water in loamy soil.