Water Harvesting

The collection and storing of water on the surface of the soil for subsequent use is known as water harvesting. This includes all measures that induce, collect, store and conserve surface runoff in the the region. Water harvesting is most essential operation in arid and semi-arid region, where water is the deficit for most of the season

Methods of Water harvesting

1. Runoff inducements
2. Land alteration
3. Chemical treatments
4. Runoff farming
5. Water spreading
6. Micro catchments
7. Dug wells
8.  Tanks
9. Farm ponds
10. Percolation tanks
11. Inter row water harvesting
12. Broad bed furrows

Rain water harvesting

The rain water harvesting refers to the process of collection and storage of rainwater for specific uses to humankind’s.

Advantages of Rainwater Harvesting

1. Rainwater is bacteriologically pure
2. It is free from organic matter and soft in nature.
3. It will help in reducing the flood hazard.
4. It will help in reducing the flood hazard.
5. It improves the quality of existing ground water
6. Rainwater may be harnessed at place of need and utilized at the time of need.
7. The structure required is simple, economical and eco-friendly.

Ground Water Recharge

Artifical recharge is the process by which the ground water is augmented at a rate much higher than those under natural condition of replenishment. The techniques of artificial recharge can be broadly categorized :

1. Direct Recharge
   1. Surface recharge
      1. Flooding
      2. Basins or Percolation tank
      3. Stream augmentation
      4. Ditch and Furrow system
   2. Sub Surface recharge
      1. Recharge Well
      2. Recharge pit
      3. Dug well
2. Indirect or Induced Recharge

Surface Recharge

These methods are suitable where large area of basin is available and aquifers are an unconfined without impervious layer above it. The rate of infiltration depends on nature of top soil. The various spreading methods are as below:

1. Flooding: This method is suitable for relatively flat topography. The water is spread as a thin sheet. It requires a system of distribution channel for the supply of water for flooding. Higher rate of vertical infiltration is obtained in areas with undisturbed vegetation and sandy soil covering.
2. Basin and Percolation tanks: This is the most common method for artificial recharge. IN this method, water is impounded in series of basins or percolation tank. The size of basin may depend upon the topography of area, (flatter area will have large basin). The most effective depth of water in basin is 1.25 m. This method is applicable in alluvial area as well as hard rock formation.
3. Stream augmentation: Seepage from natural streams is one of the most important sources of ground water recharge. The check dam or widening the steam beds increases the infiltration. In addition, the site selected for check dam should have sufficient permeable layer.
4. Ditch and furrow system. In areas with irregular topography, ditches or furrow provide maximum water contact area for recharge. This technique requires less soil preparation and is less sensitive to silting.

Sub-Surface Method

1. Recharge well. Recharge wells can be of two types
   1. Injection well, where water is pumped in for recharge
   2. Recharge well, where water flows under gravity. It is cost effective for shallow water table aquifers up to 50 m. These wells may be of dry or wet types.
2. Pits and shafts. This is Suitable where impervious layers are encountered at shallow depth. This normal diameter of shaft should be more than 2 m to accommodate more water. A silt free source water can be put into recharge pit directly through pit directly through pipes. In case of silty water, it is suitably filtered through the coarse sand passage before recharging. These structures are cost effective, least evaporative and require less land area.
3. Dug wells: The dug wells are used as recharge structure by suitably diverting storm water and surplus canal water into it. The water for recharge should be silt free and guided through a pipe to the bottom of well to avoid entrapment of bubbles in the aquifer.

Induced Recharge

It is an indirect method of artificial recharge involving pumping from aquifer hydraulically connected with surface water such as perennial streams, unlined canal or lakes. The heavy pumping lowers the ground water level and zone of depression is created. Lowering of water levels induces the surface water to replenish the ground water. This method is effective where steam bed is connected to aquifer by sandy formation.