Water Resource in India [Part 2]

July 2, 2012
By Krishiworld

The above phase of the run-off cycle pinpoints the inflow components for the surface-as well as for the ground-water resources. It has to be appreciated that there is always a balance between the inflow factors making up water resources of a region, whether surface or ground, & the outflow components.The surface water resource of a given basin in excess of the withdrawal use is accounted for on the outflow side by one or more of the following factors:

(i)Stream outflow from the basin;
(ii)loss through evaporation;and
(iii)the influent recharge to the ground water.

Similarly, the unutilised ground-water resource of a basin is accounted for by the following outflow factors:

(i)Evapo-transpiration from the ground-water-table;
(ii)outflow to the neighbouring ground-water basin;
(iii)the effluent discharge to the streams;and
(iv)the addition to the ground-water storage.

The interrelationship between the surface-water & the ground-water resources is evident from the above analysis.The surface-water resources contribute to the ground-water recharge in various ways:
(i)by influent recharge from the streams;
(ii)by seepage from natural lakes,ponds,etc;
(iii)seepage from artificial storage reservoirs,canal systems,etc, &
(iv)return flow from irrigation. These factors presently contribute to about 25 percent of the country’s total ground-water resources.

On the other hand, the bulk of the base-flow in the rivers, which represents the sustained fair-weatherrun-off is contributed by the ground-water resources. This contribution,presently, is roughly assessed at about 25 percent of the total surface-water resources of the country.

FACTORS AFFECTING WATER RESOURCES

The water resources of a region,conceived as a dynamic phase of the hydrologic cycle, are influenced by the following three major groups of factors:

    1.CLIMATIC FACTORS

  1. Rainfall : its intensity,duration & distribution.
  2. Snow
  3. Evapo-transpiration
    2.PHYSIOGRAPHIC FACTORS

  1. Basic characteristics.
    1. Geometric factors : drainage area,shape,slope & stream density.
    2. Physical factors : land use, surface infiltration conditions,soil types,etc.
  2. Channel characteristics : carrying capacity & storage capacity.
    3.GEOLOGICAL FACTORS

  1. Lithologic including composition, texture, sequenceof rock types & the thickness of rock formations.
  2. Structural, including chief faults & folds that interrupt the uniformity of occurence of rock types or sequence of rock types also beds, joints, fissures, cracks,etc.
  3. Hydrologic characteristics of the aquifers permeability, porosity, transmissivity, storability,etc

The physiographic features (including geological factors) not only influence the occurence & distribution of water resources within a region but these, particularly the orography, play a significant role in influencing rainfall & other climatic factors, such as temperature, humidity & wind. However, within a geographical location & physiographic framework, it is primarily the rainfall (its intensity, duration & distribution) & the climatic factors affecting evapo-transpiration that determine the totality of water resources in the region.

 

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