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develop mass - frequency- duration curves of streamflow records. The MFDE curves were used to predict <br />expected flow volumes for varying drought duration and recurrence intervals. A method was also <br />developed to plot the MFD curves on a semi - logarithmic versus extreme value probability scale using <br />standard spreadsheet software. <br />A concern with the partial duration analysis, particularly in areas such as the Front Range was the <br />majority of the annual water runoff that occurs over a relatively short period of time as a direct result of <br />snowmelt. The statistics for the analysis for a short drought duration of six months or less are biased by <br />the inclusion of the low flow season data in the analysis. Frequency duration analyses were conducted <br />using the Log Person Type III distribution on runoff season flow to evaluate the effect of such a bias. <br />The drought analysis results revealed that giving any period a specific drought label (e.g. the 50- <br />year RI, 24 -month duration drought) is not a clear -cut decision and can be misleading. Any such drought <br />could also be shown to be comprised of a multitude of both dependent and independent drought of shorter <br />duration and both lesser and greater severity. Rather than selecting the worst drought of record as the <br />design period for the Master Plan drought periods in the historical record were located on the MFD <br />curves. This was done to identify candidate simulation periods for modeling the City's system at <br />acceptable levels of protection defined by both duration and frequency of occurrence. <br />City of Loveland <br />In cooperation with the CWCB, in August 1986 Loveland conducted a Phase I Drought Study <br />based on a 1,000 -year synthetic monthly supply record to determine 100 -year drought conditions. The <br />study led to the enlargement of Green Ridge Glade Reservoir, which is being financed by a loan from <br />the CWCB Construction Fund. <br />The City was concerned about the systems capability to provide a firm water supply under drought <br />conditions. To address these concerns, a comprehensive water resources planning study of the City's raw <br />water supply system was conducted. This was to evaluate the ability to provide a reliable water supply <br />under drought conditions for a 30 -year planning horizon: 2) evaluate and recommend alternatives for <br />providing an emergency and firm water supply; and 3) conduct an economic feasibility study of the <br />recommended alternative. <br />Increases in raw water demands were and acquisition of additional water supplies was projected <br />for Loveland under three population growth scenarios. Two computer models were developed to simulate <br />monthly operation to the City's system. The first model (BTRIVER) simulates the diversions of the <br />City's and other water rights on the Big Thompson River. The second model (LOVESYS) simulates the <br />operation of the C -BT and windy Gap systems and then allocates raw water source to direct demand and <br />storage. Deficits are then computed were supplies are insufficient t meet demand. Using historic <br />streamflow records on the Big Thompson and Colorado Rivers and regional precipitation data, 10000 - <br />year synthetic streamflow records on the big Thompson were developed and input into the models. The <br />synthetic records allowed operational test of the system's ability to meet demands under a wide range of <br />drought conditions providing a statistical basis to characterize the objective that sufficient water supplies <br />should be developed through the year 2015 to eliminate deficits at the 100 -year recurrence interval. <br />Twelve alternatives were identified and evaluated based on their ability to reduce or eliminate the <br />projected 100 -year deficit. The alternatives included additional raw water storage, purchased/lease of <br />additional water, reuse, exchanges, water conservation, revised operations, ground water, and various <br />combinations. The evaluation process considered cost, environmental and social impacts and operation <br />constraints. Throughout the study public input was received vial monthly citizens forum meeting and <br />workshops. The recommended alternatives included the expansion of the City's reservoir and purchase of <br />additional C -BT units. Both computer models were installed and are used to periodically update study <br />results as population grows and additional water supplies are acquired. <br />Based on the planning study results the City Council approved a series of eight annual water rate <br />increases to provide revenues for bonding the expansion of the reservoir. In addition up to 50% of the <br />4 <br />