October 13, 2010

The Platte River Ecosystem, Central Nebraska

The Platte River runs across the entire state of Nebraska. Originating as the South Platte from the Colorado Rockies and the North Platte in Wyoming, they join together near Oglalla, NE.

The river was described by those on the Oregon Trail as "a mile wide and an inch deep" and lacking any trees. Essentially the water flowed over the sand and sediments laid down for millions of years. There is so much sediment, it simply could not erode a channel and flowed over the top in a massive braided river. It averaged a mile wide and was up to 2 miles wide in some places.

The movement of the sand and water made it almost impossible for trees to last long before being eroded out, so most of the valley was covered in seasonal wetlands and wet meadows. But, these seasonal wetland provided the ideal area for the largest sandhill crane populations in North America. Each year thousands of sandhill cranes descended onto the Platte River valley to nest. They are named for the Sandhills region of Nebraska afterall...

But, with the channelization and development of the river valley came changes. Higher wetlands were claimed for agriculture. Dikes straightened the path of the river. Irrigation claimed up to 70% of the water in the river. And with lower water levels and less movement of silt, trees began to invade the floodplain. The straighter channels also sped up the water's velocity, causing it to carve deeper channels.

The river is still wide and braided, but on a much smaller scale. Today, cottonwoods and willows line both sides and the islands inbetween and sandhill crane populations are just a fraction of what they once were.

By the way, there is so much water in the sands of this region that if you want a lake on your property, all you need to do is dig a big hole and water will seep right in. They are called "sandpit lakes".

But, in places the state is working on restoring the Platte to a more natural and historic setting. They are returning some farmland into wetlands and fallow fields and restoring lost prairie. Hopefully, the sandhill cranes will come back as well and the river will once again be a mile-wide and an inch deep.

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