Ground water

Surface water contained interconnected pores under the water – table of aquifers is referred as ‘Ground water’. Ground water occurs when the water flow through the impermeable surface barriers and it reach the unsaturated zone and collected by spaces that made by interconnected spaces. 

Water flow beneath the surface depends on rocks porosity and nature of the percolation. Therefore ground water limited between the specific rocks. Rocks origins that accumulated excessive water from well or spring called as aquifers. 

Zones of Ground water

Ground water zone primarily divided as saturated zone and unsaturated zone. Unsaturated zone divided as (i) soil zone, (ii) intermediate zone, and (iii) capillary fringe. This zone structure and size depends on topography, geology, drainage and components that control the location of water table. Unsaturated zone deeper in elevated land structure, percolation areas and drainage divides. 

Aquifers are in saturated zone. The surface that separate these two zones know as water table. Above the water table of an aquifer contain a layer of capillary fringe. Basement pores of capillary fringe filled with water. When the water table drop capillary fringe become wide and water table high it will shrink. It has significance contribution on the ground water recharge and discharge. 

Intermediate zone presents between the capillary fringe and the surface. Unsaturated zone located between the water table and land surface that presents with openings or pores in the soil contained unsaturated zone. 

Ground water Recharge and Discharge

Recharge is a process of ground water replenished. Recharge occurs due to the permeability rock or soil permit the water flow into the surface. Water that comes from precipitation transmit towards the aquifers is the recharge region. Water infiltrates depends on vegetation cover, slope, soil composition, depth to the water table, the presence or absence of confining beds and other factors. 

Discharge area is the opposite of recharge areas. Ground water comes interior through the recharge areas and outlet through the discharge areas. Ground water discharge occurs where the water table intersects the land surface. 

Gravity is the force that moves ground water downward from high land areas. High land areas are known as recharge areas and lowland region known as discharge areas. Aquifer has to been origin beneath the river basin. Therefore it also consider as important recharge area. 

Influence of dynamic factors on the groundwater regime

Dynamic factors can be divided into (i) Endogenous factors, and (ii) Exogenous factors. Endogenous factors are origin from processes of Earth’s crust and mantle, including tectonic movements, volcanic activities and earthquakes. The influence of earthquake takes a place of sudden movement of the water table with very high amplitude. 

Exogenous factors play an important role by ground water regime formation. They are as follow:

(    (a)   Meteorological factors:

These factors primarily include evaporation and precipitation. Ground water indirectly influenced by these  factors and also other characteristics of the atmosphere – air temperature, air humidity, cloudiness, sunshine duration and intensity and others. Some climatic factors have direct influence such as, air temperature, air humidity, cloudiness, sunshine duration and intensity and others (Walton, 1970). 

The influence of precipitation on ground water regime depends on its phase condition, duration and intensity. The meteorological factors determined by the position of the aquifer to the earth’s surface.

(     (b) Hydrological factors :

Stream water level and discharges, surface water level in water reservoirs have influence on ground water level due to the hydraulic connection between the surface and ground water exists.

     (c)    Biological factors :

Specifically, vegetation has influence on infiltration rate and velocity of infiltrating precipitation water into the soil and through rock up to ground water level. The rate of interception, transpiration and the total actual evaporation from the catchment factors also has influence on ground water.

(          (d) Space or global factors :

It includes solar activity, gravitational forces of the sun and moon, Earth’s rotation, movement around the sun and other factors.

     (e)   Human activities :

Various types of human activities affecting the ground water withdrawal (Nemethy – Fendekova, 1993). Such as irrigation, melioration, land reclamation, artificial recharge, river regulation, water reservoir construction and operation, mining, artificial loading and unloading of the surface.