The document discusses key concepts related to river discharge and hydrographs. It defines discharge as the amount of water in a river measured in cubic meters per second. Discharge increases from the source to the mouth as tributaries add more water. Width and depth also increase downstream. Factors like rainfall, temperature, and land use affect discharge. Velocity is the speed of the river measured in meters per second. A hydrograph shows changes in river discharge over time and can reveal the lag time between rainfall and peak discharge after a storm.