ANALYSIS OF HISTORICAL GROUNDWATER LEVEL VARIABILITY IN BOULDER COUNTY, COLORADO

The objective of this study is to assess future changes in groundwater resources through the analysis of historical groundwater level data. Boulder County in Colorado is the study site that encompasses mountainous regions to the west and lowland plains to the east.

We assess permitted wells in Boulder County constructed from 1950 to 2016. All well data were obtained from the Colorado Division of Water Resources including well location, depth, and static water level. Most water level data are one-time measurements. The USGS provides time series data for several wells. We detect overall changes in groundwater levels using geospatial analysis in ArcGIS. To investigate short-term shifts in groundwater levels, we evaluate the data in 10-year increments. By analyzing the groundwater level in subsets of wells of similar depths, we explore changes in groundwater resources in specific, separate aquifers of the region. Boulder County datasets from ESRL (NOAA) facilitate our analysis of groundwater level data with concurrent precipitation and temperature records. With Landsat imagery and the ENVI software platform, we examine temporal and spatial changes in urban features and land use to detect population expansion in areas of Boulder County from the 1970s to the present.

Analysis of the temporal shifts in Boulder County groundwater levels from the 1950s to 2016 reveals (1) information on current groundwater levels and (2) the associated decreases in groundwater levels with population growth and the construction of urban structures over time in the county. Groundwater level data show distinct variability in bedrock aquifers in higher elevations and alluvial aquifers in the plains in Boulder County. Changes in the groundwater levels in alluvial wells across the eastern plains of Boulder County also indicate influences of climate trends and the impact of land use conversions on the hydrogeological system.