The Colorado Water Conservation Board (CWCB) is working to update the Statewide Water Supply Initiative (SWSI), a technical analysis of water supply and demand forecasts for a wide variety of water uses across the state. The data in previous SWSI studies has informed discussions among Colorado’s nine basin roundtables, and was incorporated into Colorado’s Water Plan, published in 2015. The last SWSI was completed in 2010, but this update, planned to be completed in 2018, will look different than previous versions as it will create a more complete picture of Colorado’s future water supply outlook, with a new approach and more accessible data.

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SWSI 2010 reviewed and explored Colorado’s water demands along with the state’s infrastructure needs and gaps for the next 40 years. The analysis painted a broad picture, and while it provided many useful numbers and forecasts, it included few details on climate change and other evolving issues affecting water in Colorado.

The approach in 2010 was to obtain water usage data and plans for projects from water providers across the state and then analyze those numbers alongside population projections to determine broad potential impacts to Colorado’s water resources. Next, analysts looked at the potential gap between available water supply and municipal and agricultural demand and shared those numbers with basin roundtables around the state so that they could begin to formulate plans to bridge the gap. Though useful for planning purposes, there was concern that the data used for SWSI 2010 didn’t fully incorporate the state’s diverse water needs and complicated potential futures. Many also expressed the desire to see much more detailed data that’s specific to each basin because supply needs and issues are distinctive and vary from basin to basin—while some have large populations and a focus on municipal water availability, others focus heavily on agriculture.

To address these concerns, the current SWSI update will be much more comprehensive, focusing on  a scenario planning approach, using a variety of water supply, climate, and population projections. “We have been directed to employ a scenario planning approach, using hydrologic modeling of wet and dry years to determine potential supply gaps,” says Greg Johnson, section chief for the CWCB’s Water Supply Planning Section.

The CWCB is taking a methodical and widely-sourced approach for this update. It also has the benefit of using data collected via House Bill 1051 that began in 2014,requiring water providers to report their water data on usage and conservation. While the data submitted under this bill provides a much improved framework for data reporting there are still many gaps as there are few consequences for not submitting data.

The CWCB and the engineering firms contracted to help with the SWSI analysis are working hard to refine and implement the SWSI analyses. The team is currently incorporating a wide array of input received as a result of the Technical Advisory Group (TAG) process from local representatives of basin roundtables throughout the state. “While the analysis will be far from perfect, it will hopefully better define potential major water issues facing Colorado in years to come” Johnson says.

summer2017datahwcoverRead additional coverage on the SWSI update in the Summer 2017 issue of Headwaters magazine through the story Mapping Colorado’s Water Future.

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