Discharge

Reduced discharge: less water passes along the river, for example after a period of low rainfall or when water is removed upstream.

Discharge is relatively low because only a small area supplies water near the source and few tributaries have joined. Although the gradient is steep, the shallow water encounters considerable friction from the bed and banks. Average velocity is therefore generally lower than farther downstream, even though individual rapids can be fast-flowing.

The river has a steep gradient, but its discharge is relatively small because few tributaries have joined it. Large, angular pieces of sediment are common.

These conditions produce a short lag time and a ‘flashy’ response: river discharge can rise rapidly after heavy rain. The sudden rise is sometimes called the Tees roll or Tees wave; the river level can rise by about one metre in 15 minutes.