Question

How would rain water harvesting aid in soil conservation?

Answer 1

1) Contour bunding / trenching : A contour is an imaginary line joining different points at the same height or level. In other words, on a slope, if two points are said to lie on the same contour or contour line, it means they are at the same height regardless of where they may be located. By making bunds and trenches along a contour line (the soil dug out to make a trench is used to construct a bund on the lower side), either continuously or in an overlapping manner, the flow of rainwater is slowed, thus reducing runoff and soil erosion and allowing recharge of groundwater. After a period of time, the trenches will get filled with runoff soil which is generally fertile top soil. This soil should be periodically dug out and used for spreading out around the farm.

2) Ploughing along the contour : This has obvious benefits because the downward flow of both water and soil is arrested.

3) Mulching

4) Use of cover crops

5) Provision of swales : Swales are shallow, circular depressions around trees filled with mulch. They help direct rainwater towards the roots and also aid in reducing irrigation quantities for the same reason. The mulch also helps conserve moisture.

6) Percolation tanks and well rechargers :Percolation tanks are usually not used for irrigation purposes but hold water simply for the process of recharging ground water. Small percolation tanks scattered around a farm would help in water harvesting. Smaller circular structures around a well filled with porous materials like sand and gravel or stone chips would also help recharge open wells.

7) Making check dams : A small check dam can be constructed on a farm where slope is quite prominent. A check dam is usually made along a gully where rainwater flows in large volumes and cuts and erodes the soil. It has a silt trap just above itself where sediment in runoff water is trapped. The check dam itself is constructed with easily available local material and the aim is to slow down water flow, reduce erosion and increase percolation.

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