Chapter 3: Hydrological Processes in Riparian Areas
Transmission Losses
- Transmission losses, also called abstractions, refer to the water that infiltrates into the channel bed during stream flow.
- In semiarid regions, where many dry channels make up the drainage network, transmission losses are very significant.
- As water flows through a normally dry channel, it infiltrates into the channel (transmission loss) and reduces both the runoff volume and the peak rate of flow.
- Water lost to infiltration can contribute to groundwater recharge, and at a minimum will affect soil moisture distribution in surface sediment layers.
- EXAMPLE: A storm on August 1982 in the Walnut Gulch Experimental Watershed produced 250,000 m3 of runoff at Flume 6, with a peak discharge of 107 m3 s-1 (Figure 3.9). As stream flow moves downstream (4.2 km) to Flume 2 the peak discharge was reduced to 72 m3 s-1 and 48,870 m3 of water were absorbed in the channel alluvium. Finally, at Flume 1 6.7 km downstream from Flume 2 the peak discharge was further reduced, and 41,930 m3 of runoff was infiltrated in the channel. The decrease in peak discharge and increase in water losses was due to transmission losses along the dry channel.
Figure 3.9. Transmission losses during a summer event at the Walnut Gulch Experimental Watershed.
