Development of a Flood Detention/Stormwater Capture/Aquifer

Development of a Flood
Detention/Stormwater Capture/Aquifer
Recharge Facility in a Semi-arid Environment
Michael Milczarek, GeoSystems Analysis
Robert Rice, GeoSystems Analysis
John Wallace, PE, CFM, JE Fuller/Hydrology & Geomorphology
Cyrus Miller, PE, CFM, JE Fuller/Hydrology & Geomorphology
Karen Riggs, PE, LS, Cochise County Highway & Floodplain Division
David Goodrich, USDA-Agricultural Research Service
Lainie Levick, USDA-Agricultural Research Service
BACKGROUND
• Groundwater mining affecting flows in the San Pedro River
• Precipitation and natural groundwater recharge rates are
low (≈ 350 mm/yr; ≈ 3.5 mm/yr)
• Can flood control basins be used to capture stormwater
and increase groundwater recharge?
o How much increased stormwater runoff from
impervious areas?
o Location of detention structures to maximise affect on
river base flows?
o Design to maximise recharge and minimize
maintenance?
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Study Elements
1. In-situ monitoring to evaluate surface water infiltration
and groundwater recharge in channels and basins (5 yr)
2. Develop highly detailed surface water runoff and
infiltration model to estimate:
a) Effect of urbaniization on runoff
b) Changes in channel infiltration and groundwater recharge due to
urbanization
c) Effect of flood control basins on infiltration and recharge
3. Scale results of detailed watershed model for use in
other nearby watersheds
4. Design and implement pilot project
Project Location
GeoSystems Analysis, Inc.
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San Pedro
River
In-situ Recharge Monitoring
• Four ephemeral channel, two detention basin sites
– Install vadose monitor wells to depths of 17 meters
– Advanced tensiometers and temperature probes
– Stilling wells to measure surface water duration and depth
• In-situ field testing, inverse modeling
• Estimate groundwater recharge rates from 5 years of
data (indirect methods)
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Estimated Recharge Rates
• Average channel flow 115 hours/year (184 hours max)
• Majority of recharge from high precipitation periods.
• Estimated annual groundwater recharge rates of
– 0.3 m to 3.5 m per year (channels)
– 0.3 m to 1.6 m feet per year (basins)
• Average in-situ channel recharge rates ≈ 2X increase
resulting from urbanization
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Runoff/Infiltration Modeling
• Approx elevations 1250
to 2750 m amsl
• Precipitation is
bimodal, elevation
dependent (300 to 600
mm/yr)
• Develop AGWA/
KINEROS model for
Coyote Wash (5200
hectares)
• Scale Coyote Wash
model to other
watersheds (13; 40,000
hectares)
Coyote
Wash
AGWA/KINEROS2 Modeling
• Physically based, extensive input parameters
• Model individual events from 45 year precipitation record
• Different model runs to predict stormwater runoff and
infiltration from:
– pre-urbanized vs urbanized conditions,
– w/ and w/o detention basins
– high and low permeability basins
• Use stormwater infiltration/groundwater recharge
relationships from monitoring data to estimate potential
changes in groundwater recharge (recharge functions)
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Each plane assigned
parameters:
• soil infiltration rate
• land cover
• impervious percent
• runoff parameters
Modeling Results
• Post-urban conditions are estimated to increase channel
groundwater recharge rates 2X to 3X
• Adding stormwater flood control/recharge basins may
increase recharge another 2X (4% to 6% of precipitation)
• Model needs calibration!
• 16 regression equations (250K data points) describe
model output as function of:
– Precipitation depth and season (Summer, Other)
– Percent impervious surface
– Basin and channel permeability
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Paired Watershed Study vs Regression
Model Results
Pilot Project Approach
• Need to reduce flooding in Palominas watershed (1950
ha (9.75 ha of channels))
• Identify optimum areas for stormwater capture and
groundwater recharge
• Detention basin design to:
– Reduce peak flows to pre-urbanized flows
– Reduce sediment load
• Recharge basin design to optimize stormwater capture
and recharge
• Monitoring to quantify recharge benefits
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Target Areas for Deeper Investigation
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Mansker Detention/Recharge Basin Design
Recharge basins
Detention basin
Orifice Plates
Existing Channel
Spillway
Predicted Stormwater Capture and
Groundwater Recharge at Mansker
Scenario
Precipitation
Record
(years)
Base case capture (up to 28800 m3/event)
Additional Capture - 78 Dry Wells
Additional Capture - 26 Infiltration Trenches
1.5X additional detention capture
2X additional detention capture
3X additional detention capture
56.9
Estimated
Average
Percent
Percent Avg Annual
Annual
Increase in
of Total Groundwater
Runoff
Groundwater
Recharge
Runoff
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Recharge
Captured (m )
3
(m )
209000
51%
96140
242000
59%
129140
34.3%
231000
57%
118140
22.9%
255000
63%
117300
22.0%
285000
70%
131100
36.4%
318000
78%
146280
52.2%
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Pilot Project Design
• Site near to river (< 2 km), shallow groundwater (≈ 12
m bgs)
• Stormwater detention basin (10,000 m3 capture)
o Orifice plates to meter flow, reduce sediment loads
• Downstream recharge basins (9,600 m3 capture)
• Estimated recharge cost ≈ $1.75 m3
• In-situ monitoring system to determine:
o
o
o
o
Surface water inflow – outflow
Effect of drywells and infiltration trenches
Effect on groundwater elevations
Temperatures and moisture contents at various depths
• Use results to apply to other watersheds!
Proposed
Monitoring
U
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She she!
mike@gsanalysis.com
Land Cover Types
Legend
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