andrew streitz minnesota pollution control agency · introduction ydescribe baseflowstudy. yshare...
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Andrew Streitz Minnesota Pollution Control AgencyMinnesota Pollution Control Agency
IntroductionDescribe baseflow study.Share results of analytic review of flow data.Review complicating issues.Provide update on recently completed, integrated SWAT/MODFLOW d l f h Li l R k C k SWAT/MODFLOW models for the Little Rock Creek Watershed.
B flBaseflow
Definition from the USGS: baseflow is that part of streamflow that is sustained primarily by groundwater discharge It is not attributable to direct runoff from discharge. It is not attributable to direct runoff from precipitation or melting snow.
Flow‐duration hydrographs
A cumulative frequency curve that shows the f i h ifi d di h percentage of time that specified discharges are
equaled or exceeded.
Straight River
GagingGagingstation dataset
Determining trends in flow.
Two measures1) Statistically significant trends via Mann‐Kendall non‐parametric trend tests; andp ;
2) Sign test analysis of all trends2) Sign test analysis of all trends.
High Island Creek Summer flowHigh Island Creek‐ Summer flow1,000
July Dischargeh
600
800
cfs
August Discharge
400
600
Disch
arge‐c
200
D
Statistically Significant Discharge Trends
01990 1995 2000 2005 2010
Statistically Significant Discharge Trends
Di t ib ti f Si ifi t T dDistribution of Significant Trends
Red‐ Statistically SignificantDecline in July andJ yAugust Flows
Blue‐ No significant trend
Summer July August
Trends in Flow: July &Flow: July & August1991 ‐ 2011
Hydrologic ContextPrecipitationAnnual mean flowHigh capacity water withdrawalsField tiling
MN Annual Precipitation
No trend
S th t MN P i it ti D tSouthwest MN Precipitation Data:1991 ‐ 2010
30
35
25
30
tion (in.)
20
25
Precipitat
15
Southwest Precipitation 5 yr running Avg
1990 1995 2000 2005 2010
Minnesota Statewide WaterMinnesota Statewide Water Appropriations Data
300
250
ons/year)
Statistically Significant Increasing Trends , p= 0.001
200Billion gallo
150thdraw
als (B
Groundwater consumptive use
100
5
Total W
it Groundwater, consumptive use
Surface Water, consumptive use
1990 1995 2000 2005 2010
Field Tiling
Bois de Sio atershedBois de Sioux watershed
Little Rock Creek Watershed
Minnesota Test Case forMinnesota Test Case for Groundwater Management?
Little RockRock Creek StudyArea
Model boundary
G d t P i i th W t h dGroundwater Pumping in the Watershed
300
400
200
300
on g
allo
ns
100
Milli
o
01990 1995 2000 2005 2010
Statistically significant to p= 0.01
Groundwater LevelsGroundwater Levels
01990 1995 2000 2005 2010
2
Observation well 5004
4
w groun
d
6
Feet below
8
10
Statistically significant decline, p= 0.01
Phase 2 Coupled Surface Water &Phase 2‐ Coupled Surface Water & Groundwater models
Baseflow Conclusions
Baseflow in Minnesota streams is undergoing statistically significant declining trends;P i i i d b iblPrecipitation does not appear to be responsible;Groundwater & surface water withdrawals do appear to be partially responsible and the increased installation be partially responsible, and the increased installation of field tiling may be a factor;Detailed groundwater/surface water modeling at a Detailed groundwater/surface water modeling at a pilot watershed provides us with tools to manage the use of water resources while protecting stream ecology.
The End