2.1 Basic hydrology

Small rivers are important they are lifelines..

Hydrology Hydrology is defined as the study of the movement, distribution, and quality of water throughout the earth, and addresses both the hydrologic cycle and water resources.

Hydrological cycle The hydrological cycle describes the continuous movement of water on, above, and below the surface of the earth. Since the water cycle is truly a "cycle," there is no beginning or end.

Hydrological Cycle

Water balance Water balance is defined as the balance between the inflows, outflows and change of storage in any water body over a period of time. A water balance can be used to help manage water supply and predict where there may be water shortages The following slides wil show more on water balance

Water Balance - incoming water Rain, rivers, groundwater…

Water Balance – outgoing water Evapotranspiration (ET), outflowing rivers, groundwater flows…

Stream flows peak also, but..

Water balance formula In = out (+ change in storage) In: Rain, rivers, groundwater flows Out: drainage, runoff, groundwater flows, ET Storage: groundwater change

Sustainable vs unsustainable situation In a sustainable situation the inflow equals the outflow. What happens in an unsustainable situation when too much water is pumped?

Rainfall comes in peaks

Overdraft Groundwater table drops, pump can not reach it, aquifer depletes, crops die…

Eventually… You can make deeper bore holes, but water table keeps dropping…

Overdraft When groundwater is pumped faster than the recharge, water levels drop Porous media lose water, pores are filled with air Porous media could consolidate, resulting in land subsidence, sink holes, loss of water storage capacity