Question

It is important to make small check dams across the flooded guillies because they
i. Hold water for irrigation
ii. Hold water and prevent soil erosion
iii. Recharge ground water
iv. Hold water permanently
A. i and ii
B. ii and iii
C. iii and iv
D. ii and iv
E. i , ii and iii

Answer 1

Hint: Check dams are traditionally implemented in two different environments. They are across the channel bottoms and hilly slopes. They are primarily built to control the water velocity, conserve soil, and improve the land

Complete Answer:
- A check dam is a small, occasionally temporary, dam constructed across a swale, drainage ditch, or waterway to counteract erosion by dropping water flow velocity. Check dams themselves are not a kind of new technology. Somewhat, they are an ancient technique dating from the second century A.D.
- Check dams are usually, though not always, implemented in a system of several dams located at regular intervals across the area of interest. A check dam placed in the ditch, swale, or channel interrupts the flow of water and flattens the gradient of the channel, thus decreasing the velocity.
- A gully is a landform formed by running water, eroding harshly into soil, usually on a hillside. Gullies look like large ditches or small valleys, but are metres to tens of metres in intensity and width. When the gully formation is in progression, the water flow rate can be considerable, causing a major deep cutting action into soil.
- Gullies diminish the productivity of farmland wherever they slit open into the land, and produce sediment that may clog downstream water bodies.
- A major part of water stored following dams in the world is withdrawn for irrigation, that is, evaporation and transpiration needs. Water used in surplus of evaporation and transpiration needs appears in the system as exterior or groundwater.
- The total quantum of flow and size and frequency of peak floods in the flood season decreases in the downstream due to a dam, reducing flood hazard due to flood of land, crop and property. It also reduces congestion of runoff in plains and coastal lands. Any soil erosion such as gullies by now formed can be tackled by the building of dams or obstructions.

So the correct answer is option E.

Note: Check dams are generally small, and are temporary buildings made across the canal. They are generally constructed to slow down the velocity of the flowing concentrated water. And also it is a practice which helps to reduce the erosion.