Droughts



Prairies are maintained by cycles of drought and fire, which prevent woody vegetation from dominating the landscape. In Kansas, droughts have been a regular part of the climate since time immemorial, and help to shape not only our terrestrial ecosystem but our rivers as well. Droughts can benefit prairie streams by reducing populations of non-native, harmful plants and animals. They can also concentrate prey in small pools, providing a bonanza to predatory fish and birds. However, severe and prolonged droughts can stress fish and other aquatic animals, and if flows are too low for too long there may be population crashes and even extinctions from parts of the river system. Once flows return to higher levels, fish can return as long as there are no damns, weirs, or other barriers to movement.


Weather records extending back to the 1890's show clearly that wet and dry periods are fairly common, and that in the recent past dry spells have been more severe and have persisted for a longer period than in recent times. This record is a warning to water managers in the state who are planning for the possibility of severe and prolonged droughts in the future.


The USGS monitors river levels in Kansas using a variety of state-of-the art equipment. At a recent meeting of the Watershed Restoration and Protection Strategy coordinators, USGS personnel explained how they install and maintain monitoring equipment that continuously measures flow levels. This "real time" information can be used by the public to find flow rates for different river reaches, which can be especially useful when planning float trips on the Kaw. You can find the latest flows at the USGS Waterwatch website.


How much water flows in a river is a function of how much rain falls on the land, but it also depends on groundwater connectivity. This picture of the Arkansas River at Great Bend shows what can happen to a river when groundwater is depleted by irrigation. The Arkansas River has been the subject of long-term disputes between Kansas and Colorado over groundwater depletion, but similar problems occur in portions of the Smoky Hill-Republican-Kansas River system.

The Google Map below is interactive, if you click on the icons you can see the stream flows during various periods of droughts over the past century. You can also see the precipitation amounts by clicking on the blue storm clouds. 

Data source: 2000 - 2006 Flows at some USGS streamgages lower than 1930's or 1950's droughts

 



The yellow icons mark stream flows that follow the pattern you would expect-- that is, flow is lower in years with severe droughts than in other years with either normal rainfall or minor droughts. The orange icons mark stream flows that are lower than you would expect-- in recent years, since the onset of heavy irrigation, the flows are lower than they were in the severe droughts of the 1920's and 1950's. This indicates that we have manmade drought conditions in these streams that are having an adverse impact on aquatic organisms like fish and mussels.


The stream gage on the Neosho River demonstrates the expected pattern-- stream flows are lowest when precipitation is lowest.


The Arkansas River shows what happens when the groundwater becomes depleted-- droughts have been made much worse in recent decades because there is less groundwater entering the stream to supplement flows.

This depleted "manmade drought" pattern can be seen in the Smoky Hill River as well, which is a major tributary of the Kaw.