Northern Integrated Supply Project Environmental Impact Statement South Platte River near Kersey Stream Morphology Technical Report Prepared for: U. S. Army Corps of Engineers Omaha District March 2008 Prepared by: ERO Resources Corporation 1842 Clarkson Street Denver, Colorado 80218 (303) 830-1188 CONTENTS 1. Introduction .................................................................................................................1 1.1. Northern Integrated Supply Project ................................................................1 1.2. No Action Alternative .....................................................................................1 1.3. Group 1—Southern Group ..............................................................................2 1.4. Group 2—Northern Group ..............................................................................3 1.5. Group 3—Eastern Group ................................................................................4 1.6. Independent Participants .................................................................................6 1.7. Action Alternatives—Activities Common to All Alternatives .......................8 1.8. Alternative 2—Proposed Action—Glade Reservoir and the SPWCP ..........10 1.9. Alternative 3—Cactus Hill Reservoir and the SPWCP ................................11 1.10. Alternative 4—Glade Reservoir and SPWCP with Agricultural Transfer Lands ..............................................................................................12 2. Study Area ................................................................................................................13 3. Methods.....................................................................................................................13 4. Environmental Conditions ........................................................................................14 5. Environmental Consequences ...................................................................................16 5.1. Alternative 2 (Applicant’s Proposed Action) ...............................................17 5.2. Alternative 3..................................................................................................17 5.3. Alternative 4..................................................................................................18 6. Mitigation and Recommendations ............................................................................18 7. References .................................................................................................................18 TABLES Table 1. Peak discharges for the South Platte River near Kersey ...............................15 FIGURES Figure 1. NISP Service Areas and No Action Alternative Figure 2. Alternative 2 (Applicant’s Proposed Action) - Glade Reservoir and South Platte Water Conservation Project (SPWCP) Figure 3. Carter Pipeline - No Bureau of Reclamation Contract Alternative Figure 4. Alternative 3 - Cactus Hill Reservoir and SPWCP Figure 5. Potential Agricultural Transfer Lands (Portion of Alternative 4) i Figure 6. Average daily flows, South Platte River near Kersey (USGS gage 06754000), 1901–2004. Figure 7. Total annual flow volumes, South Platte River near Kersey (USGS gage 06754000), 1901–2004. APPENDIX Appendix A. Alternatives 2 and 3 Flow Duration Curves ii NORTHERN INTEGRATED SUPPLY PROJECT SOUTH PLATTE RIVER NEAR KERSEY STREAM MORPHOLOGY TECHNICAL REPORT 1. INTRODUCTION The U.S. Army Corps of Engineers (Corps) is preparing an environmental impact statement (EIS) for the proposed Northern Integrated Supply Project (Project or NISP). As part of the EIS, this technical report has been prepared to describe existing conditions and potential effects of the Project alternatives on stream morphology resources. The information gathered in this technical report will be summarized in the EIS. 1.1. Northern Integrated Supply Project The proposed Project is a collaborative effort among 12 water providers (Participants) facilitated and coordinated by the Northern Colorado Water Conservancy District (District). The Project will provide approximately 40,000 acre-feet (AF) of new reliable water supply, which will meet a portion of the Participants’ estimated 2025 and 2050 additional water supply needs. The Participants are a group of rapidly growing communities and domestic water districts located throughout the District. The Project would be a nonfederal project constructed and owned by the District. While the District would retain ownership and operational responsibility of the Project, the Participants would own a perpetual contractual right to a defined portion of the project facilities and a defined portion of the water diverted by the Project. 1.2. No Action Alternative The No Action Alternative considers what the Participants would do to meet their water supply needs in the absence of NISP. In the absence of NISP, obtaining new water supplies in the region likely would become more challenging as demand for a finite supply of sources would increase. Because it is not possible to determine the specific mix of future water development approaches that would be pursued by the individual Participants or the region as a whole (the process of acquiring water supplies would be driven by complex social, economic, environmental, and political factors), the No Action Alternative is conceptual, and is intended to represent the possible water supplies that each Participant could obtain. 1 NISP SOUTH PLATTE RIVER NEAR KERSEY STREAM MORPHOLOGY TECHNICAL REPORT For the NISP No Action Alternative, Participants were grouped based on factors such as geographic proximity, common sources of existing supply, likely pursuit of the same new sources of supply, and obvious advantages from shared conveyance and storage facilities (HDR 2007a). Four Participants (CWCWD, Evans, FCLWD, and Fort Lupton) were not grouped because implementation of the No Action Alternative could most effectively be accomplished independently given their locations, water systems, and supplies. The Participants were grouped for development of the No Action Alternative as follows (Participant firm yield demands from NISP are identified in parentheses): GROUPED PARTICIPANTS Group 1– Southern Group • Erie (6,500 AF) • Lafayette (1,800 AF) • Lefthand Water District (4,900 AF) Group 2 – Northern Group • Eaton (1,300 AF) • Severance (1,300 AF) • Windsor (3,300 AF) Group 3 – Eastern Group • Fort Morgan (3,600 AF) • Morgan County Quality Water (1,300 AF) INDEPENDENT PARTICIPANTS • Central Weld County Water District (8,400 AF; this includes Berthoud’s prior contract right that has been obtained by Frederick, which is served by CWCWD) • Evans (1,600 AF) • Fort Collins-Loveland Water District (3,000 AF) • Fort Lupton (3,000 AF) 1.3. Group 1—Southern Group Group 1 (Southern Group) includes the Towns of Erie and Lafayette, and the Lefthand Water District (Figure 1). 2 NISP SOUTH PLATTE RIVER NEAR KERSEY STREAM MORPHOLOGY TECHNICAL REPORT 1.3.1. Erie Erie is located in the Boulder Creek drainage, which has very limited water rights purchase and transfer potential due to prior acquisition by other municipalities. Current sources of supply include Colorado-Big Thompson (C-BT) units and shares in local mutual irrigation companies. 1.3.2. Lafayette Lafayette is located within the Lefthand Creek and Rock Creek drainages. Current sources of supply include C-BT units and shares in local mutual irrigation companies. 1.3.3. Lefthand Water District The Lefthand Water District (LHWD) is situated in the Lefthand Creek and St. Vrain Creek drainages. Current sources of supply include C-BT units and shares in local mutual irrigation companies. 1.3.4. No Action Alternative for Southern Group Under the No Action Alternative, the likely sources of new supply for the Southern Group would include: • Purchase and transfer of agricultural water from ditches such as the South Boulder Canyon Ditch, the Leyner and Cottonwood #1 Ditch, the Lower Boulder Ditch, the Coal Ridge Ditch, the Leggett Ditch, the Boulder and Weld County Ditch, and the FRICO—Community Ditch. Many of the ditches in this area are to a significant extent controlled by conservation easements by Boulder County Open Space. These easements restrict the water’s use to irrigation purposes, precluding transfers to municipal use. Such arrangements must not be overlooked in identification of potential supplies. • Under the No Action Alternative, at least 10,800 AF of storage would be required for the Southern Group. The most probable means of providing storage would be through development of gravel pit lakes. The most likely scenario would be 10,800 AF of gravel pit storage along Boulder Creek downstream of Boulder or St. Vrain Creek downstream of Longmont, with 270 to 360 surface acres (assuming a depth of 30 to 40 feet) represented by 2 to 4 pits (typical pits are in the 100 to 200 acre range). To augment evaporation losses, assuming 1.5 feet of annual evaporation, an additional 405 to 540 AF of water would be required. • Purchase of C-BT units, which continue to decrease in availability and increase in cost. 1.4. Group 2—Northern Group Group 2 (Northern Group) includes the Towns of Eaton, Severance, and Windsor. 3 NISP SOUTH PLATTE RIVER NEAR KERSEY STREAM MORPHOLOGY TECHNICAL REPORT 1.4.1. Eaton Eaton is located north of Greeley, and current sources of supply include C-BT units and shares in local mutual irrigation companies. Eaton currently uses Horsetooth Reservoir as storage for the water it receives