Hydrology is the scientific study of the movement and distribution of water on Earth. The water cycle is driven by energy from the sun, which causes evaporation of water from oceans, lakes, rivers, and soil into water vapor in the atmosphere. Water vapor then condenses to form clouds and precipitation falls back to the ground through rain or snow, completing the cycle. A hydrograph provides information on discharge, maximum and minimum run-off, average run-off, and total discharge volume during a given period by showing the flow rate over time.

1. Hydropower Engineering
Lecture 3
School of Electrical &
Computer Engineering

2. Hydrology
 Hydrology is the scientific study of the movement, distribution,
and quality of water on earth and other planets, including the
water cycle, water resources and environmental watershed
sustainability.
 Hydrologic cycle. : the sequence of conditions through which
water passes from vapor in the atmosphere through precipitation
upon land or water surfaces and ultimately back into the
atmosphere as a result of evaporation and transpiration.
 The water cycle is driven primarily by the energy from the sun.
This solar energy drives the cycle by evaporating water from the
oceans, lakes, rivers, and even the soil.
 Other water moves from plants to the atmosphere through the
process of transpiration.
 The hydrologic cycle begins with the evaporation of water from
the surface of the ocean.

3. Cont’…
 There are four main stages in the water cycle. They
are evaporation, condensation, precipitation and collection.
Let's look at each of these stages.
 Evaporation: sun causes water from oceans, lakes, streams, ice
and soils to rise into the air and turn into water vapour (gas).

4. Cont’…

5. Cont’…
 A hydrograph provides the following information:
 The discharge at any time during the period under
consideration.
 The maximum and minimum run-off during the period.
 The average run-off during the period.
 Total volume of discharge up to any time, given by the area
under the curve up to that time.

6. THANK YOU