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<br />k <br /> <br />o <br /> <br />of this inventory is to provide a framework for understanding the "big picture" <br />interrelationships between South Platte surface water and groundwater resources <br />and various conservation, reuse, groundwater development and conjunctive use <br />options being considered by Denver area water providers. The SB74 Study's <br />computer-based interactive tool is helpful in understanding the numerical <br />information presented in this chapter. <br /> <br />. <br /> <br />Key points: <br />1. Undeveloped flows or developable flows are significant in above average <br />runoff years. Most of the developable flows occur below the metro <br />Denver area. (Figs 1-17 to 1-1 9 Chapter 1 , Technical Addendum No.1) <br /> <br />2. Additional reservoir storage or ASR (Aquifer Storage and Recovery) <br />would allow the use of these developable flows. <br />3. Platte River Three State Cooperative Agreement would need to be <br />implemented in order to meet Endangered Species Act requirements <br />associated with future use of the developable flows. <br /> <br />Chapter 3 - Estimate of the Impact on Runoff to the South Platte River from <br />Construction of Impervious Surfaces in the Denver Metropolitan Area for the <br />Period 1950-1995 (Technical Addendum No.1, Chapter 4) <br /> <br />This chapter describes an analysis of the increase in South Platte River gains <br />through the Denver metropolitan area over the past several decades as a result <br />of urbanization. The approach used to estimate the increased stream flow gains <br />assumes the gains have resulted primarily from (1) runoff from impervious <br />surfaces (RIS), and (2) lawn irrigation returri flows (L1RF). <br /> <br />. <br /> <br />Key points: <br />1. Based on preliminary research, the non-reusable increase in runoff from <br />impervious surfaces was approximately 52,000 acre-feet and the non- <br />reusable lawn irrigation retum flows was approximately 21,000 acre-feet, <br />or a total of approximately 72,000 acre-feet. <br />2. The total streamflow gain from urbanization is approximately 0.10 cfs per <br />1,000 persons, or 72 acre-feet/year <br />3. Some Peer Review Group members suggest this increase in runoff <br />should be considered as an offset to Denver Basin aquifer pumping <br />impacts. <br />. 4. Additional studies are needed to more accurately quantify the amount <br />and timing of increases in runoff from impervious surfaces. <br /> <br />Chapter 4 - Inventory of Existing Water Efficiency Practices (Technical Addendum <br />No.1, Chapter 2) . <br /> <br />-6- <br />