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:
Image Source: nca2014.globalchange.gov
1. Climatic Factors:
A. Rainfall: its intensity, duration and distribution.
ADVERTISEMENTS:
B. Snow
C. Evapo-transpiration
2. Physiographic Factors:
A. Basic Characteristics.
1. Geometric Factors: drainage area, shape, slope and stream density.
ADVERTISEMENTS:
2. Physical Factors: land use, surface infiltration conditions, soil types, etc.
B. Channel Characteristics: carrying capacity and storage capacity.
3. Geological Factors:
A. Lithologic including composition, texture, sequence of rock types and the thickness of rock formations.
B. Structural, including chief faults and folds that interrupt the uniformity of occurrence of rock types or sequence of rock types also beds, joints, fissures, cracks, etc.
ADVERTISEMENTS:
C. Hydrological characteristics of the aquifers permeability, porosity, transmissivity, storability, etc.
The physiogrpahic features (including geological factors) not only influence the occurrence and distribution of water resources within a region but these, particularly the orography, play a significant role in influencing rainfall and other climatic factors, such as temperature, humidity and wind. However, within a geographical location and physiograhic framework, it is primarily the rainfall (its intensity, duration and distribution) and the climatic factors affecting evapo-transpiration that determine the totality of water resources in the region.