Introduction and water balance
Using an illustration, define the components of the hydrologic cycle.
What are the three sub-systems of the hydrologic cycle? What are the hydrologic
components in each sub system
State and discuss the water balance equation (s) used in hydrological studies
annual discharge at the outlet of a catchment is 0.5 m
/s. The catchment is situated
in a desert area (no vegetation) and the size is 800 km
. The average annual precipitation is 200
Compute the average annual evaporation from the catchment in mm/year.
In the catchment area an irrigation project covering 10 km
is developed. After some years
the average discharge at the outlet of the catchment appears to be 0.175 m
Compute the evapotranspiration from the irrigated area in mm/year, assuming no change in
the evaporation from the rest of the catchment.
A catchment has a size of 100km
. In its original condition, the average annual total runoff
from the catchment is 1.1 m
/s. the average annual rainfall is 800 mm/year. In an average
year, 50% of the rainfall infiltrates and 12.5% of the rainfall reaches the groundwater. Tests
have turned out that the average annual evapotranspiration from the unsaturated zone
amounts to 340 mm/year. Evapotranspiration in this case is the sum of transpiration and the
bare soil evaporation. Assume that storage effects are small and therefore can be neglected.
Using a well-illustrated diagram show all the water balance components for this
How much water, in mm/year, reaches the root zone through capillary rise in an average
How much water, in mm/year, seeps out from the groundwater to the surface water in
an average year?
How much water, in mm/year, evaporates directly from interception in an average year?
How much, in mm/year, is the total evapotranspiration in the catchment in an average
For the same catchment in Question 1(a), there is a plan to install a well field that will
withdraw 0.16 m
/s from the catchment for drinking water consumption elsewhere. As a
result, the groundwater level is expected to go down and capillary rise into the root zone will
no longer be possible. The percolation is expected to remain the same.