I wanted to share this informative email, forwarded to us, this week by Sue Peters:
-----Original Message-----
From: Smith, Richard - NRCS-CD, Hayti, SD [mailto:richard.smith@sd.nacdnet.net]
Sent: Monday, December 19, 2011 4:44 PM
Subject: Lake Poinsett Update Dec 19,2011
Checking in one last time for 2011.
For many Lake Poinsett residents 2011 will be one they would like to forget, but no doubt never will. No predictions of next year yet, but a few items that will have an impact on water issues. The watershed is in a far different position than last year. Hamlin county is officially listed as experiencing a drought which started in July and continues. The soil profile is extremely dry versus last year being in a saturated condition. The small sloughs and wetlands are empty with only the larger ones having surface water at freeze-up time. The upper lakes have quit overflowing or nearly so, which adds some early capacity. Summing this all up, it will take a lot more snow and/or rain than last year's near record amounts to create a repeat of 2011 problems.
Always in need of a good story to relate to others, may I provide you with some material. Don't try to read all this on your Blackberry.
From the first time I experienced flooding conditions at Lake Poinsett I was always suspicious about why it took so long for water to exit Poinsett and get into the Big Sioux River. Water would rise in March often peak in April and then stay above flood levels until late July or August or later. Looking at the topography and elevation drop from the outlet of Poinsett to points below Estelline, one can understand that it is relatively flat and maybe that explains enough it. Knowing that the Big Sioux River already flowing full makes it difficult to fill the river even more from Poinsett gives reason for the slow outflow also. Some surmise that the reason is the roads and bridges between Poinsett and the Big Sioux River that throttles back the flow, although we never see evidence of water blockage (higher on upstream side vs. downstream side) at any of those suspected sites. Others comment that because the channel is filled with vegetation it causes a slow down, but the water moves in a definite channel with adequate capacity and it does not have vegetation in the main channel. Even the gate system is sometimes blamed, but again, we never see any elevation difference of up or downstream water at the gates when open. Something I did discover this Fall and received supplemental information on was that the Ordinary High Water Mark established on Lake Poinsett is truly determined by a high point in the outlet channel nearly 3/4 of a mile downstream from the flood gates. Yes, the lake shore used to go that far and still does when full. An old line of rock mark this site which is visible north of the bridge 1/2 mile North and 3/4 mile East of the flood gates. This realization dismisses any thoughts that the sill of the flood gates impedes the flow or that a deeper channel to the lake would make a difference. The water would still have to climb that natural ridge to get out and water doesn't climb!
I'm going to give Darvin Holter (North Lake Drive) credit for putting me on to something else. He suggested that something at the point of where the Outlet channel of Poinsett and the Big Sioux River met may be causing a problem, although he didn't really know what the nature of the problem was other than the way the river and channel bend together. In early June I hiked into the general area which is approximately one mile from any road, but with the flood conditions it all just looked like one large lake and was even hard to distinguish where the channels were located. Later in the summer I found aerial photos taken in 2010 (with lower water levels) showing an abrupt change in the direction of water as it entered the Big Sioux River. Because the Big Sioux River water was muddy and the Poinsett water was clear, one could see that Poinsett water was meeting Big Sioux River water head to head before they both turned and went down the river mixed. In September after finding that information I contacted the landowner for permission to access the site by field roads and in turn he drove me back in and offered some fascinating information.
Prior to 1911, Sioux Falls Power and Light owned the property. I was able to confirm that through the Register of Deeds, but no mention of anything else as far as improvements or structures when the property changed hands in 1911. The landowner related an old family tale that the power company had built a diversion dam across the Big Sioux River to channel water into Poinsett in the spring and then it would supply the Big Sioux River throughout the summer months with water to run water wheels and generators all along the river going south. This information coming after hearing of all the low head dams that still exist on the BSR (several drowning attributed to them), it was completely believable.
When we approached the site in September with low water flows, it was obvious that indeed a rock structure was present but the extent of it didn't impact me until I realized it was some 8 ft plus in height and over 100 ft long. The landowner said that he was told that farmers dynamited a large portion of it across the river to get rid of it at one time. Much of the rest of it had for years silted in was barely visible without probing the grass to find the rock. Since no rock exist for several miles in this area, one can only imagine the work to bring all the rock in by horse and hand place each of the 20 to 50 pound rocks used. Some old wood pilings still remained and no doubt provided some sort of additional gating. While the portion across the BSR was either gone or not visible, it was still plain to see that water was deflected so that it had to try to flow against the BSR to get out of the outlet channel.
It would have been interesting trying to calculate the hydrologic effect from the energy dissipated from the two water forces meeting. Only through some type of modeling will we ever know the measurable effect as the structural impact was removed last Wednesday. While it only took a day to dismantle, the paperwork and contacts with Corps of Engineers, USDA, Cultural Resource, Northern Prairies Land Trust, East Dakota Water Development District and the Lake Poinsett Water Project District took a couple of months until I could give the contractor a go ahead.
Going forward the only thing to expect (or hope for) from this endeavor is to shorten up the time that flood conditions remain on Poinsett after a flooding event. Nothing has changed in the elevations of Ordinary High Water, how deep the outlet channel or Big Sioux River is or even maximum height that Poinsett might reach during a quick fill.
Season's Greetings to All of You and Hope for an Enjoyable New Year!
Rick Smith
North Central Big Sioux River/
Lake Poinsett Watershed Coordinator
PO Box 165
Hayti, SD 57241
605-783-3353
