Science in the Upper Mississippi River Basin by SJzq4AJ

VIEWS: 4 PAGES: 17

									         Summary of Streamflow Conditions
           and USGS Low-Flow Activities

            State Drought Task Force Meeting
                     March 29, 2012
                  St Paul, MN - Webinar

               James Fallon, Dave Lorenz, Greg Mitton
                     USGS, Mounds View, MN

            jfallon@usgs.gov               763-783-3255
U.S. Department of the Interior                   Photo of dry channel at
U.S. Geological Survey                Minnesota River at Montevideo, 1932
                      Topics
    • Summary of Streamflow Conditions
    • Mississippi Low-Flow Report Findings
    • Low-Flow Statistics & Web Resources
    • Low-Flow Triggered Activities
      – Extra low-flow measurements
      – Mississippi River GW Seepage Study between
        St Cloud and Elk River


                                    Le Sueur River near Rapidan
2
                                    Sept. 28, 2011 31 cfs
           Summary of Streamflow
               Conditions
    1. Background: snowmelt peaks are often greatest
         flows of year for northern 2/3’s of Minnesota
    2.   Most streams have peaked due to snowmelt
    3.   Peaks are about 1-month earlier than usual
    4.   Most peaks are smaller than normal
          Typically about 25th percentile
          Some flows extremely low but masked from season
    5. Spring rains could change all this

3
                                              Overview
    Much of US experiencing below-normal streamflow



         Northern US gages not reporting: ice-affected




4   http://waterwatch.usgs.gov/new/index.php?id=dryw     http://waterdata.usgs.gov/usa/nwis/rt
    Minnesota Flow Conditions Similar

                                                            First glance: flows seem normal
                                                            with low flows in south & NE

                                                            Look closer at hydrographs
                                                               with respect to season
                                                               and timing




5   http://waterdata.usgs.gov/mn/nwis/current/?type=intro
    Flow-Duration Hydrographs from
         Selected Streamgages

                                             Basswood 8
                                                                     7 Pigeon
                                                              5Kawishiwi
                                                 7 Prairie
      Red-Fargo 8
                       7 Buffalo
                                           7 Miss-B

                                                   7 1. Snake current


          MN-Monte 8             Crow 8            7 Miss-Anoka
                                               7MN-Jordan

                           LeSueur 8                       7 Straight
                                 7 DesMoines


6      WaterWatch Duration Hydrographs http://waterwatch.usgs.gov/new/index.php
       Current Streamflow Conditions http://waterdata.usgs.gov/mn/nwis/current/?type=flow
    So what do these low-flow conditions look like?
            Mississippi River Low Flow
                      Report
                                                                   




       “Normal” snowmelt runoff peak at Le Sueur River near Rapidan,
7      March 23, 2007. Measured 3,260 cfs after peak (trees on left bank).
    Mississippi River Low Flow
              Report
                                                      




                                      Cobble Riffle




    Same view of channel last fall.
    September 28, 2011. 33 cfs




8
    Flow this spring: March 7, 2012. Just past snowmelt runoff peak.
    Peak was <1,000 cfs (about 1.5 ft higher than shown in picture).
    View looking upstream of same cobble riffle.

9
Low-Flow Characteristics of
the Mississippi River



Research supported by the
Met Council (2008)
Dave Lorenz and Erich Kessler
USGS Minnesota Water Science Center
                                      http://pubs.usgs.gov/sir/2010/5163/
 Study Objective and Approaches
Characterize the regional low flows in the Mississippi
River upstream of Minneapolis.


Part 1. Review low-flow duration statistics for the Miss. R.
near Anoka, one upstream site (Grand Rapids), and three
tributaries (Crow R., Crow Wing R., and Rum R.) as well
as the headwaters reservoirs.


Part 2. Construct a very large sample of potential flows,
by superpositioning observed summer flows on
observed snowmelt flows.
  Implications, Part 1
1. The greatest threat from low flows occurs when the
   Mississippi River near Anoka and the upstream
   basins experience low flows.
2. The assumption that droughts and corresponding low
   flows are widespread is not necessarily true. There
   are several instances of low flows in one or two
   basins and not in the other basins.
3. In general, the headwaters reservoirs are at or below
   their summer operating range during lowest flows in
   the Mississippi River.
Approach, Part 2
30000
                                                              Flow.1976
                                                              Flow.2003
                                                              Synthetic Flow
25000



20000



15000



10000



5000



   0
        Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec
Implications, Part 2
  The greatest threat from the lowest flows
  occurs before the end of June when a dry
  spring follows a snowmelt peak of less
  than 11,300 cubic feet per second.
       Low-Flow Triggered Activities

     1. Discharge
        measurements at
        low-flow sites
     2. Mississippi River
        Groundwater
        Seepage Synoptic
        Measurements


15
       Additional Drought Resources
     Drought-related Web Page               Low-Flow Statistics Web Page




     http://mn.water.usgs.gov/drought/   http://mn.water.usgs.gov/infodata/lowflow/
16
                       Questions?
     1. Snowmelt peaks are often greatest flows of year
          for northern 2/3’s of Minnesota
     2.   Most streams have peaked due to snowmelt
     3.   Peaks are about 1-month earlier than usual
     4.   Most peaks are smaller than normal
           Typically about 25th percentile
           Some flows extremely low but masked from season
     5. Many conditions in Upper Mississippi Basin
          “right” for severe low flow in Metro
     6.   Spring rains could change all this
17

								
To top