Water table “window”

When it rains is just as important as how much.

Case in point can be found in the Neches River Basin in the Big Thicket region of Texas.

The long term average shows that it rains about the same every month there, right around 5 inches per 30 days, for an annual total of around 55 inches.

That might lead you to believe that the rivers flow evenly all year round as well.

Instead, the rivers surge to their annual high water marks in late spring followed by a drop down into low flow conditions (called base flow) during the late summer.

The missing ingredient is evapotranspiration.

During summer, the thick carpet of plants and sizzling sun suck up every last drop of rain that falls. That leaves just “base flow” crumbs for the rivers and streams.

Come winter the window into the water table opens wide. These are the “soaking in” rains that replenish the aquifer and discharge into the rivulets that feed the cricks that feed the streams that empty into the rivers.

An exception is made for the really really big rains:

When they fall in the Big Thicket, they find their way to the river any time of year!

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