TECHNIQUES FOR DEVELOPING AN EFFECTIVE FIELD MONITORING PROGRAM FOR GROUNDWATER DATA IN THE SOUTH PLATTE BASIN OF NORTHEAST COLORADO

The Colorado Water Conservation Board, the State’s water resources planning agency, has embarked on a 6-year program to develop the South Platte Decision Support System (SPDSS) for management of the basin's water resources. Heavy use of the South Platte River and hydraulically connected alluvial aquifer for irrigation and increasing use of bedrock groundwater for municipal supplies result in groundwater being a key and very dynamic element in the region’s water resource portfolio. The groundwater component of the SPDSS project includes the four main bedrock aquifers of the 6700-square mile Denver Basin, and the 3000-square mile South Platte River alluvial aquifer system and its tributaries.

Developing a groundwater field data collection and monitoring program for such a large region poses significant challenges with a limited budget. To accomplish this, the project started with an extensive effort to collect, analyze, and map available published information on aquifer configuration, aquifer properties and groundwater levels. For the field component, an initial phase of well drilling and aquifer testing was undertaken to fill immediate data gaps, done with cooperation of water user groups and municipalities in the study area. For the second phase of the SPDSS, a review of the project goals and corresponding data needs to meet those goals was performed, with an emphasis placed on collection of water level and groundwater flux information. The resulting shift in emphasis has led to a modified well drilling program, a doubling of the water level monitoring program and increased effort in collecting data on streambed permeability, stream channel geometry, and methods to estimate baseflow. These field data, in conjunction with existing groundwater data for the region gathered in the first phase, will provide an efficient and cost-effective method to help characterize the resource for future modeling and planning purposes for this major river basin.