Texas rivers are important, not only for their beauty
and recreational value, but also as habitat for a diversity of animal life.
But few people realize that an entire community of unusual animals lives beneath the river
bottom. The water-filled spaces between river cobbles
make up a barely-known habitat that biologists call the hyporheic zone: a big word that simply
means ‘beneath the river’. The hyporheic zone is a transition between
the stream habitat, and a deeper, groundwater habitat. As the boundary between these two habitats, the hyporheic zone contains animals from both.
These include aquatic invertebrates that you can find by flipping rocks in your nearest
stream. Such as crayfish and mayflies
The hyporheic zone also includes groundwater invertebrates that are blind and without pigment,
like animals that you might expect to find in caves, such as snails and small crustaceans, including amphipods and isopods. Many of these species are found in Texas and nowhere else on earth. To understand the small lifeforms that live in the hyporheic zone, biologists use a special
piece of equipment called a Bou-Rouch pump, which consists of a hollow spike that is driven
into the hyporheic zone. Once the spike is in place, a hand pump is
attached to the top. Groundwater is pumped out and filtered through
a net, which collects the invertebrates that live in the hyporheic zone. Once pumping is
complete, the Bou-Rouch pump is removed, and no lasting damage is done.
Biologists at Texas Parks and Wildlife are just beginning to study Texas’ hyporheic zone,
one more unique habitat that is part of our rich, natural heritage.