Point Bars and Cottonwoods
by Gene Gade
THIS
IS KEYHOLE DAM ON THE BELLE FOURCHE RIVER IN NORTHEAST WYOMING.
IT
WAS WAS CREATED TO PROVIDE WATER STORAGE FOR IRRIGATION AND FLOOD CONTROL DOWN
STREAM.
IT
ALSO PROVIDES RECREATION AT THE RESERVOIR:
THE DAM DOES ALL OF THOSE THINGS.
NOT
SURPRISINGLY, DAMS LIKE KEYHOLE AFFECT THE ECOLOGY ALONG THE STREAM BELOW IN A NUMBER OF WAYS.
MOST
PRAIRIE RIVERS ACTUALLY HAVE MORE MATURE, STABLE AND DIVERSE PLANT AND ANIMAL
COMMUNITIES THAN THEY HAD BEFORE DAMS, HOWEVER THERE ARE TRADEOFFS.
BEFORE
DAMS, PRAIRIE RIVERS OFTEN FLOODED IN
THE SPRING AND NEARLY DRIED UP IN THE LATE SUMMER.
SPRING
FLOODS MEANDERED ACROSS WIDE FLOOD PLAINS, CHANGING CHANNELS FREQUENTLY AND
ERODING CUT BANKS LIKE THIS ON THE OUTSIDE OF RIVER BENDS.
AND
SAND-GRAVEL POINT BARS LIKE THIS ON THE INSIDE OF THE CURVE.
COTTONWOOD
AND WILLOW SEEDLINGS NEED POINT BARS FOR THEIR ESTABLISHMENT.
AGE,
DISEASE, FIRE, AGRICULTURAL ACTIVITIES, BROWSING BY WILD ANIMALS, AND CHANGING
WATER TABLES TAKE THEIR TOLL ON THE OLDER COTTONWOODS AND THE SPECIES
ASSOCIATED WITH THEM.
ONCE
IN A WHILE, STREAMS LIKE THE BELLE FOURCHE NEED A HIGH WATER EVENT TO FLUSH
THEM OUT AND RENEW THEM. I'M GENE GADE
OF THE UNIVERSITY OF WYOMING COOPERATIVE EXTENSION SERVICE.