If the streamflow has been measured regularly over a long period, including times of drought and flood, the studies are greatly simplified.
Streamflow is highly variable, being greatest during the wet summer months and considerably less in the relatively dry winter.
As forests regrow following cutting, increases in streamflow decline as a result of increased transpirational losses.
Conservation reservoirs store water from wet weather periods for use during times of drought and low streamflow.
The absence of snowpack in the south Indian uplands makes the region dependent entirely on rainfall for its streamflow.
From streamflow data, determinations can be made of the minimum, maximum, average daily, and average monthly flows; the size of dams, spillways, and downstream channel; and the seasonal and carry-over storage needed.
If adequate streamflow data are not available, the streamflow may be estimated from rain and snow data, or from flow data from nearby streams that have similar climatic and physiographic conditions.
Streamflow is perennial, averaging more than 10 inches (250 mm) in depth per stream each year.
The water yield of a forest is a measure of the balance between incoming precipitation and outflow of water as streamflow.
It has a higher density and viscosity than a streamflow and can deposit only the coarsest part of its load; this causes irreversible sediment entrainment.
Drought, also spelled drouth, lack or insufficiency of rain for an extended period that causes a considerable hydrologic (water) imbalance and, consequently, water shortages, crop damage, streamflow reduction, and depletion of groundwater and soil moisture.
