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SWSI & Water Supply Update 
DWR > Documents & Forms > Reports and Publications > SWSI & Water Supply Update

About SWSI 

The Surface Water Supply Index (SWSI) developed by this office and the U.S.D.A. Natural Resources Conservation Service is used as an indicator of mountain-based water supply conditions in the major river basins and sub-basins of the state.  The SWSI compares the total volume of water in a basin or sub-basin against the volume available in the same month of historical years.

SWSI Map Tools

Map Viewer (CDSS)  To view the SWSI map layer, open MapViewer (CDSS) and, in "Map Layers", check the "Surface Water Supply Index (SWSI)" layer.  To change which month's SWSI is being viewed, expand the layer by clicking on the + on the left and then check/uncheck individual months as desired.

SWSI Tabular Datasets   Colorado Information Marketplace (CIM)Tools include new tabular data for SWSI.  Choose a link below

1. Surface Water Supply Index by HUC:  Monthly SWSI values on a sub-basin (HUC8) level. 

2. Surface Water Supply Index Component by HUC:  Volume of water available to individual structures within each HUC.  This data is used to calculate the SWSI value. 

3. Surface Water Supply Index by Basin:  Monthly SWSI values on a basin level. 

SWSI Reference Material 

SWSI Documentation Files 

SWSI Modeling Files


The Colorado water Supply Conditions Update Reports are produced by DWR on a monthly basis.  The reports incorporate Division-specific information and the month’s SWSI analysis to produce a comprehensive review of water conditions for each of Colorado’s seven river basins.

2019 Monthly Reports

2018 Monthly Reports

All Monthly Reports