Extensive Investigation of Intermittent Streams Indicates Link to Past Climate
A new USGS study published in the journal River Research and Applications presents an extensive analysis of temporary (intermittent) streams across regions in the conterminous United States where such streams are prevalent (in the western plains and southwest) and describes their sensitivity to past climate.
Understanding how intermittent streams may be changing is important because they often serve critical — albeit impermanent — roles in supplying recharge to aquifers, transferring snowmelt water to perennial streams, accumulating agricultural and municipal effluents, and maintaining aquatic biological diversity downstream, to name a few examples.
Five distinct types of intermittent streams with record lengths of generally over 40 years and with minimal direct human influence were identified for this study based on their seasonal patterns of no-flow periods. Each type of stream had a different mixture of the physical processes that generated no-flow events. These processes included the timing of precipitation, antecedent soil-moisture conditions, snowmelt, and evaporation. Notably, the duration of wet and dry periods were found to affect the seasonality of streamflow at intermittent streams, but the intensity of precipitation events had little effect.
The temporal patterns of streamflow regimes at these intermittent streams were shown to closely reflect climatic patterns. However, the lack of trends in historical variations in precipitation at natural watersheds for this investigation has produced no clear trends in flows at intermittent streams. Nevertheless, the sensitivity of streamflows to variability in precipitation suggests that potential future drying and wetting patterns in precipitation would impact streamflows at intermittent streams.