Letter to the Editor

Water problem 6

Monday, October 5, 2009

Dear Editor,

Problem #6 with the Model - Base Flow Percentage Exaggerated

Base flow is the amount of water oozing from the aquifer into streams. Stream flow is base flow plus run off from precipitation events. Base flow cannot be greater than the total stream flow.

According to the Model, the majority of the base flows happen within a few days of a precipitation event. That means, according to the Model, precipitation is very closely tied to the amount of water coming out of the aquifer. This is not something that most people will find to be a fair or accurate definition.

To fully realize the very close tie in time between precipitation and base flow in the Model, it is really helpful to have a number of graphs and charts. On the WaterClaim site, we posted these in color so they are easy to read.

Hydrologists use formulas to estimate how much of the water in a stream comes from runoff and how much seeps out of the aquifer. There are no actual measurements. Effectively, they use a rolling average based on 3 to 5 days in order to smooth out stream flow spikes, then call everything else base flow.

Aquifers that are not close to the stream, either in horizontal or vertical proximity, do not cause a change in flow within a few days or weeks of precipitation events.

Should rain that enters the ground and then exits the ground to the stream within a few days be defined as base flow? The Model says, "Yes." If the answer were "no," then about two thirds of what the Model defines as base flow would instead be classified as run-off. The consequence of the Modeler's formula is to assign to irrigation the flows that are really associated with precipitation.

To correct the problem requires that the Model formulas be adjusted to reduce the effect of precipitation events on base flows. Again, this will not be agreed to by Kansas and should never have been accepted by Nebraska in the first place. The only possible way to correct this problem is to have the US Supreme Court order a correction. That requires either the Nebraska Governor or Attorney General to make the request.

Steve Smith,



Respond to this story

Posting a comment requires free registration: