Input Data - Base Flows

The RRCA estimates the base flow for 15 different sites on the Republican River and its tributaries since 1918.  Here we look at two of the points where stream gage data exists back before any development. 

Base flow is the amount of water oozing from the aquifer into the streams.  Base flow cannot be greater than the total stream flow.

The base flow data comes from the Nebraska Department of Natural Resources via an open records request.  The data is stored in a file labeled 12p_4rch_baseflows.rch.   It contains the base flow input data used by the Model to calculate compliance with the Republican River Compact Agreement with Kansas.

The stream flow data comes from the USGS at http://waterdata.usgs.gov/

Here we plot the base flows used by the Model against the stream flows.  Base flows used by the computer simulation that governs Nebraska's compliance are obviously much higher than stream flows.  The further one goes back the greater the spread.  These creates a serious problem.  It means that historic base flows are artificially high.  It also means that when we compare historic base flows to current base flows that the drop attributed to groundwater pumping is inflated. 

There is an actual drop in stream flows in the Republican River Basin but the data fed into the simulation exaggerates the reduction in base flow by a large amount.  The simulation compares base flows from 1918 to base flows now and assigns the difference to depletions caused by groundwater pumping. 

It is possible that the modelers have corrected the input data since it was released via the Open Records Act request in 2005.  However, there is no indication that has happened.