Reservoir Drought Operations Kevin J. Landwehr, P.E., D.WRE Chief, Hydrology and Hydraulics Branch 4 March 2013
Purpose Awareness of Drought Contingency Plans 2012/13 Reservoir Operations Drought Management Measures Scenario Analysis
Rock Island District Saylorville Lake Lake Red Rock Coralville Lake
Reservoir Summary Began Operations in: 1958 (Coralville) 1968 (Red Rock) 1977 (Saylorville) Primary Authorized Purpose: Flood Risk Management on the Des Moines, Iowa, and Mississippi Rivers Other Authorized Purposes: Provide low flow augmentation, recreational opportunities, and natural resource management opportunities.
Storage Allocation Spillway Design Flood 891.03 Surcharge Capacity Full Flood Control Pool 88.4 to 93.3% of Total Storage Volume Flood Control Storage Normal Conservation Pool (all year, except fall pool raise) 6.7 to 11.6% of Total Storage Volume Conservation Storage and Contracted Water Supply (Saylorville only)
Saylorville Water Supply Contract Contracted storage sold to the State of Iowa (1982). Sub-allocated to the Des Moines Water Works (2/3) and Alliant Energy (1/3). Provides for an undivided 18.86% of the usable storage between elevation 812 and 836 ft (projected to be 14,900 acre-ft after 25 years of sedimentation). Based on most recent survey, contracted storage is 12,300 acre-ft. State can order releases through outlet works or could construct facilities to directly withdraw from the lake.
Drought Management Integrated Component of the Water Control Manuals Drought schedule developed in coordination with State of Iowa Water supply has priority over water quality/conservation releases
Conservation Release Targets Saylorville Lake 200 cfs Coralville Lake 270 cfs 150 cfs Lake Red Rock 300 cfs
Drought Response Activities Level I II III IV Activity Monitor- stream flow, storage, rainfall, climate ***Normal Reservoir Operations*** Reduce release to base, activate CDMC, increase flow measurements, evaluate gate leakage and reservoir facilities, notify concession operators ***Actively Augmenting Releases*** Further reduction of release, increase CDMC meetings, activate IDMC, evaluate storage for emergency water needs ***Reduced Water Quality / Conservation Release with Full Water Supply Release*** Further reduction of release, allocate water for emergency needs, increase meetings of IDMC ***Water Supply Release Only***
Drought Index Levels Triggers Condition Today LEVEL Coralville Saylorville Red Rock I Always Always Always II Inflow < 150 Inflow < 200 Inflow < 300 III Pool < 678 Pool < 827 Pool < 734 IV Pool < 677 Pool < 823.5 Pool < 730
Hedging Rules for Saylorville Reservoir II III IV Condition Recommended Reservoir Release Pool elevation > 827 Release all water supply and water quality demands. 826 < Pool Elevation < 827 Release 100 percent of water supply, maintain 175 cfs at dam, and 245 cfs at SE 14th Street. 825 < Pool Elevation < 826 Release 100 percent of water supply, maintain 150 cfs at dam, and 220 cfs at SE 14th Street. 824 < Pool Elevation < 825 Release 100 percent of water supply, maintain 125 cfs at dam, and 195 cfs at SE 14th Street. 823.5 < Pool Elevation < 824 Release 100 percent of water supply; maintain 100 cfs at dam, and 170 cfs at SE 14th Street. 819 < Pool Elevation < 823.5 Release 100 percent of water supply; no water quality releases made. 816 < Pool Elevation < 819 Release 75 percent of water supply; no water quality releases made. Pool Elevation < 816 Release 50 percent of water supply; no water quality releases made.
Deviation Directive In response to low-water on the Mississippi River, directed to deviate from the water control plan to store additional water (up to 10% of flood storage) to be used for future augmentation of Mississippi River flows to support navigation. Due to low inflows at all projects, no significant storage was possible. Did not impact water available for conservation releases. Directive suspended prior to flood season.
837 836 835 Elevation (feet) 834 833 Saylorville Pool 832 831 830 829 800 600 Saylorville Outflow F low (cfs) 400 200 0 Saylorville Inflow -200 Aug Sep Oct Nov Dec Jan Feb Mar 2012 2013
743.2 743.0 742.8 Elevation (feet) 742.6 742.4 742.2 742.0 Red Rock Pool 741.8 741.6 2,500 2,000 Red Rock Outflow F low (cfs) 1,500 Red Rock Inflow 1,000 500 0 Aug Sep Oct Nov Dec Jan Feb Mar 2012 2013
684.5 Coralville Pool 684.0 Elevation (feet) 683.5 683.0 682.5 1,800 1,600 F low (cfs) 1,400 1,200 1,000 800 Coralville Inflow Coralville Outflow 600 400 200 0 Aug Sep Oct Nov Dec Jan Feb Mar 2012 2013
Drought Management Measures Deviations from Hedging Rules Deviation to Retain Fall Pool Raise or Minimal Pool Raise Recommend maintaining any pool rise due to precipitation, NTE 0.5 ft above conservation pool Long Term - No Spring drawdown of Coralville? Reduction in Outflows prior to Trigger Point Sale of Water for Consumptive Use Requires State Emergency Declaration Approval level depends on amount: < 100 Acre-ft - District 100-500 Acre-ft - Division 500+ - ASA (CW) Historical Perspective No requests
The target releases are not prescriptive, but rather intended as general guidance in setting reservoir releases. The releases are subject to revision during any particular drought event should a different response prove more beneficial. Recognize need to coordinate departures from Drought Contingency Plan hedging rules with State of Iowa. BLUF for Winter 2012/2013 Scenario Analysis and climate conditions indicated no major changes to current water management operations were needed.
Saylorville 865 860 855 850 Elev (ft) 845 840 835 830 825 Jan Mar May Jul Sep 2012 2013 SAYLORVILLE-POOL 1974 FLOW-0 ELEV SAYLORVILLE-POOL 1976 FLOWS0 ELEV SAYLORVILLE-POOL 1989 FLOW-0 ELEV SAYLORVILLE-POOL 1999 FLOW-0 ELEV SAYLORVILLE-POOL 2003 FLOW-0 ELEV
Saylorville Reasonable Worst Case 834 832 830 Elev (ft) 828 826 Flow (cfs) 824 822 820 200 180 160 140 120 100 80 60 40 20 Dec Jan Feb Mar Apr May 2012 2013 SAYLORVILLE-POOL WORSE CASE0 ELEV CP2 WORSE CASE0 FLOW CP1 WORSE CASE0 FLOW Note: late April cut to 90 cfs plan calls for 0 cfs water quality release.
Red Rock Worst Case 744 742 740 Elev (ft) 738 736 734 732 730 728 300 250 Flow (cfs) 200 150 100 50 0 Jan Mar May Jul Sep 2012 2013 RED ROCK-POOL WORSE CASE0 ELEV CP1 WORSE CASE0 FLOW CP2 WORSE CASE0 FLOW
Coralville Worst Case 684 683 682 Elev (ft) 681 680 679 678 677 676 140 120 Flow (cfs) 100 80 60 40 20 Dec Jan Feb Mar Apr 2012 2013 CORALVILLE-POOL WORSE CASE0 ELEV CP3 WORSE CASE0 FLOW CP4 WORSE CASE0 FLOW
Identification of Water Users and Potential Impacts Users Identified from: Historical reports Existing knowledge/relationships Iowa DNR withdrawal permits Users contacted to determine: Nature of constraint (flow, stage, etc.) Critical Threshold Nature of Impact Possible River Alternatives Current actions or condition (are needs being met)
Downstream Water Users
Identification of Water Users and Potential Impacts Users Identified from: Historical reports Existing knowledge/relationships Iowa DNR withdrawal permits Users contacted to determine: Nature of constraint (flow, stage, etc.) Critical Threshold Nature of Impact Possible River Alternatives Current actions or condition (are needs being met)
865 Saylorville 860 855 850 Elev (ft) 845 840 835 830 825 Jan Mar May Jul Sep 2012 2013 SAYLORVILLE-POOL 1974 FLOW-0 ELEV SAYLORVILLE-POOL 1976 FLOWS0 ELEV SAYLORVILLE-POOL 1989 FLOW-0 ELEV SAYLORVILLE-POOL 1999 FLOW-0 ELEV SAYLORVILLE-POOL 2003 FLOW-0 ELEV
834 Saylorville Lake 833 832 Observed 831 830 829 828 Worst Case / Inflow Recession 827 826 Trigger for reducing outflow 825 824 823 822
Pool Recovery Winters of 1988/1989 and 1989/1990 832.31 836.11 7 days 832.63 836.25 7 days Storage between 829.5 and 836.0 ~ 15,000 cfs-days (~ 0.1 of runoff from 5,823 sq. mi. basin)
BUILDING STRONG
Monthly rainfall distribution for Fort Dodge, IA BUILDING STRONG
For More Information: Kevin Landwehr, P.E., D.WRE Chief, Hydrology and Hydraulics Branch Rock Island District, USACE 309-794-5310