Garrison Dam/Lake Sakakawea Project North Dakota Surplus Water Report
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Garrison Dam / Lake Sakakawea, North Dakota US Army Corps of Engineers Omaha District Garrison Dam/Lake Sakakawea Project North Dakota Surplus Water Report December 2010 Surplus Water Report Cover Sheet Garrison Dam / Lake Sakakawea, North Dakota GARRISON DAM / LAKE SAKAKAWEA PROJECT, NORTH DAKOTA SURPLUS WATER REPORT Omaha District U.S. Army Corps of Engineers December 2010 Surplus Water Report Cover Sheet Garrison Dam / Lake Sakakawea, North Dakota GARRISON DAM / LAKE SAKAKAWEA, NORTH DAKOTA SURPLUS WATER REPORT December 2010 Prepared By: The U.S. Army Corps of Engineers, Omaha District Omaha, NE Abstract: The Omaha District is proposing to temporarily make available 100,000 acre-feet/year of surplus water (equivalent to 257,000 acre-feet of storage) from the sediment storage portion of the carryover multiple use zone of the Garrison Dam / Lake Sakakawea Project, North Dakota to meet municipal and industrial (M&I) water supply needs. Under Section 6 of the Flood Control Act of 1944 (Public Law 78-534), the Secretary of the Army is authorized to make agreements with states, municipalities, private concerns, or individuals for surplus water that may be available at any reservoir under the control of the Department. Terms of the agreements are normally for five (5) years, with an option for a five (5) year extension, subject to recalculation of reimbursement after the initial five (5) year period. This proposed action will allow the Omaha District to enter into surplus water agreements with interested water purveyors and to issue easements for up to the total amount of surplus water to meet regional water needs. During the temporary period, a permanent reallocation study may be conducted to address the potential for permanent changes in allocation of storage to the authorized purposes of the Garrison Dam / Lake Sakakawea Project, including municipal and industrial (M&I) water supply. The Proposed Action (temporary use of surplus water) will not impede the capability and function of Garrison Dam / Lake Sakakawea to serve its authorized purposes. An Environmental Assessment, which is attached to this Surplus Water Report, identifies the baseline environmental conditions and provides an analysis of potential impacts from the proposed use of surplus water. There are no significant environmental impacts associated with implementing the proposed action. For more information contact: Commander, U.S. Army Corps of Engineers Attn: Ms. Kayla Eckert-Uptmor, Chief, Planning Branch, Omaha District 1616 Capitol Avenue, Omaha, NE 68102-4901 Phone: (402) 995-2693 Fax: (402) 995-2758 Surplus Water Report Cover Sheet Garrison Dam / Lake Sakakawea, North Dakota Surplus Water Report i Garrison Dam / Lake Sakakawea, North Dakota EXECUTIVE SUMMARY The Omaha District, U.S. Army Corps of Engineers (Corps) under the Operation & Maintenance Program has prepared this Garrison Dam / Lake Sakakawea, ND, Surplus Water Report to identify and quantify whether surplus water is available in the Project, as defined in Section 6 of the 1944 Flood Control Act. Surplus water agreements with water users derived from this process may be executed with existing and potential future applicants, pursuant to policy, upon approval of this Report by the Assistant Secretary of the Army (Civil Works) and completion of required NEPA coordination. The term of the proposed temporary surplus water use is for a five (5) year period, renewable for an additional five (5) year period, subject to recalculation of reimbursement after the initial five (5) year period. This Surplus Water Report and accompanying Environmental Assessment investigate the engineering and economic feasibility and environmental effects of temporary use of up to 100,000 acre-feet/year of surplus water (257,000 acre-feet of storage) from the sediment storage portion of the carryover multi-purpose zone of the Garrison Dam / Lake Sakakawea Project. Surplus water, if available, may be used to meet existing and projected municipal and industrial (M&I) water supply needs in the region. The 100,000 acre-feet/year of yield (257,000 acre-feet of storage) evaluated for surplus water use in this report is an estimate that was selected to ensure that an adequate quantity of water was identified to meet the needs of existing and future M&I water users. This Surplus Water Report will serve as the basis to enter into surplus water agreements until such time as a permanent reallocation study can be completed. A 10-year study period has been established for this surplus water study. The length of the study period was selected for several reasons. First, surplus water agreements may be executed for a five (5) year period, renewable for an additional five (5) year period. Second, prior to the end of the 10-year study period, it is anticipated that a reallocation study of the six Federal reservoir projects within the Missouri River basin (including the Garrison Dam / Lake Sakakawea Project) will be completed, which will determine if changes to the permanent allocation of storage among the authorized project purposes and modifications to existing Federal water resource infrastructure may be warranted. Third, the primary water demand driving regional water needs at this time is the North Dakota oil and gas industry. Industry and state estimates indicate that demand from this industry is temporary and will decrease significantly after 10 years. The surplus water agreements executed upon the approval of this Report will serve as measures to address temporary water needs of the region during the 10-year study period. The Garrison Dam/Lake Sakakawea Project is a unit of the comprehensive Pick-Sloan Plan for development in the Missouri River Basin. The operation of the upper Missouri River’s six mainstem reservoirs and the lower Missouri River’s levees and navigation channel provides for flood control, navigation, irrigation, hydropower, municipal and industrial water supply, fish and wildlife, water quality, and recreation. The temporary use of 100,000 acre-feet/year of surplus water in Lake Sakakawea would result in net annual depletions of 527 acre-feet from the system for the ten year period, because all but 527 acre-feet of the 100,000 acre-feet/year in water use will come from the Missouri River under both with and without project conditions. The primary difference between with and without project conditions is the location of the water withdrawals. Under without project conditions (No Action), the vast majority of withdrawals will come from the free-flowing reaches of the Missouri River upstream of Lake Sakakawea. Under with project conditions (Proposed Action), withdrawals will come from the Garrison Dam / Lake Sakakawea Project. Surplus Water Report ii Garrison Dam / Lake Sakakawea, North Dakota The Daily Routing Model (DRM), developed during the 1990’s as part of the Missouri River Mainstem Reservoir System Master Water Control Manual Review and Update Study (Master Manual), was used as an analytical tool in this study to estimate the hydrologic effects that an additional 527 acre-feet of depletions would have at Lake Sakakawea, the other system reservoirs, and free-flowing reaches of the Missouri River. A comparison of DRM simulated water surface elevations, stream flows, and river stages between without project conditions and a depletion of 527 acre-feet from Lake Sakakawea (with project conditions) was performed to assess the magnitude of changes resulting from the proposed temporary use of surplus water from the Project. Modeling results indicate that stage and flow reduction estimates throughout the system are extremely small, because all but 527 acre-feet of the 100,000 acre-feet/year in surplus water will come from the Missouri River under both with and without project conditions. Because the Missouri River projects are operated as an integrated system taking into account system withdrawals both in and outside of the Federal projects, no changes to system operations will be required as a result of the temporary use of surplus water from the Garrison Dam / Lake Sakakawea Project. The method used to estimate the cost to the surplus water user for the capital investment of surplus water in the Garrison Dam/Lake Sakakawea Project is the updated cost of storage method, because it results in a greater value than benefits foregone by the temporary use of surplus water, revenues foregone, or replacement cost of the water. The relationship between reservoir storage and provided yield was calculated as 2.57, indicating that 257,000 acre-feet of storage (1.079% of total usable storage) would be required to provide a yield of 100,000 acre- feet/year. The reasonable annual price for the use of surplus water is determined by the same procedure used to determine the annual payment for an equivalent amount of storage annualized over a 30- year period plus an estimated annual cost for operation and maintenance, repair, replacement, and rehabilitation (OMRR&R). Annual payments for these surplus agreements are based on a 30-year payment schedule and the repayment interest rate identified in EGM 11-01 Federal Interest Rates for Corps of Engineers Projects for Fiscal Year 2011. The appropriate interest rate is the Water Supply Interest Rate based on PL 99-662. The FY 11 interest rate is 4.25%. The annual payment for the updated cost of temporary surplus water ($35,383,148 over a 30-year period at an interest rate of 4.25%) is $2,022,804. The total annual cost of storage, including the annual estimated OMRR&R costs allocated to the surplus water storage ($67,733), is $2,090,537 which is an annual cost of $8.13 per acre-foot of surplus water storage at FY 2011 price levels (equivalent to $20.91 per acre-foot of yield). The actual annual price for any surplus water agreement will be calculated based upon the appropriate price level for the fiscal year in which the surplus water agreement is signed.