Gilcrest/LaSalle Pilot Project: High Groundwater Issues
Landowners in the Gilcrest/LaSalle area have relayed their concerns about high groundwater levels to state officials. Several residences within the Town of Gilcrest have been impacted by groundwater entering basements. The Division of Water Resources (DWR) and Colorado Water Conservation Board (CWCB) are conducting a study of the hydrologic factors that influence the groundwater environment in this area. The agencies have undertaken an effort to compile historical groundwater level data, monitor current groundwater levels and characterize the hydrogeology within the area of interest. Brown and Caldwell have recently been contracted to analyze this data and other relevant information. The objective of their analysis is to identify relationships between the climate, geology, hydrology, and water management of the area and groundwater levels. The final report from Brown and Caldwell is found below in the Studies Section.
Preliminary information and data obtained from DWR’s investigation is updated monthly and will be posted on this website for public access.
November 2015 CSU Monitoring Wells
Colorado State University staff are collecting water level measurements from three monitoring wells to the east of Gilcrest. These water levels are plotted against precipitation and dewatering well pumping from the Lorenz well over the same time period. These graphs will continue to be posted here as they are available to DWR staff.
June 2016 Town of Gilcrest
Town of Gilcrest staff are also collecting water level measurements from wells throughout the town and at the waste water treatment plant. These water levels are plotted on a graph and also indicate periods of dewatering well pumping. This information will be updated as new data becomes available to DWR staff.
August 2016 Climate Data
Precipitation is one of the main hydrologic inputs that influence groundwater recharge and thus the groundwater levels. To provide some perspective for the groundwater level data presented, we include graphs of precipitation from the Northern Colorado Water Conservancy District’s (NCWCD) Gilcrest #105 station, located southwest of Gilcrest between the Western Mutual and Farmer’s Independent Ditch, and Greely West #224, located southwest of Greeley and north of the US Highway 34 by-pass.
To provide a broader perspective, we have plotted the monthly total precipitation at the NCWCD stations starting in November 2011. For that period of record, the spring of 2016 saw an average amount of precipitation. The winter was relatively wet and showed higher than average monthly precipitation. The final graph is the Palmer Hydrological Drought index produced by the National Climatic Data Center for the Platte River basin through 2015. Negative indexes in red represent drought years. The index is only updated annually, but shows the higher than normal precipitation in 2014 and the drought of 2012.
August 2016 Groundwater Level Data
One of the initial tasks identified in the scope of work for this project was the compilation of existing water level data and the implementation of a water level monitoring program. We have identified a number of entities that have both historic water level data and are currently collecting water levels from wells within their networks.
Central Water Conservancy District has been conducting water level monitoring since the early 1990s. While most of their measurements are from active irrigation wells, they have also installed a few dedicated monitoring wells. We greatly appreciate their assistance and cooperation in both providing data for this investigation and volunteering staff resources for expanded data collection.
We have also identified four existing irrigation wells that were part of the former Colorado State University (CSU) water level monitoring network. We have renewed monitoring in these wells as well as those that are part of Central’s network, collecting manual data on a monthly basis. We greatly appreciate the assistance and the cooperation from the respective well owners.
In addition to manual groundwater level measurements, numerous wells in the area have been equipped with electronic instruments that measure and record water levels at specified time intervals.
- The U.S. Geological Survey had two dedicated monitoring wells that were installed as part of their National Water-Quality Assessment (NAWQA) Program. One of the wells (NAWQA #7) was subsequently compromised, but we were able to supply local USGS staff with a data logging transducer to capture continuous water level measurements in their remaining well, NAWQA #11.
- Additionally, the Colorado Department of Agriculture (CDA) has a series of monitoring wells within the study area that are also equipped with data logging transducers. We are very grateful for their cooperation in data sharing for this project.
- As part of the monitoring efforts implemented for the South Platte Decision Support System, the Colorado Water Conservation Board installed three DSS wells in Beebe Draw that are equipped with data logging transducers.
- Three new monitoring wells were installed by Ryan Bailey of CSU (in section 27, T4N, R66W) and equipped with data loggers as part of a dewatering project associated with the Town of Gilcrest. Additionally, Dynotek has loaned the Division of Water Resources a datalogger and transducer, which has been installed in the south well of the Gilcrest waste water treatment plant.
Our earliest water level data date back to 1930. Project specific groundwater level information from monthly manual measurements has been collected since October 2012. To provide some perspective for the groundwater level data presented herein, a study area map is included that shows the locations of all of the wells in which we are currently collecting groundwater levels. Different colors and symbols are used for the different agency network wells. For geographic reference, we have produced hydrographs for wells and organized them by township starting in the northeast of the study area. Water level data are graphed on an axis as depth below ground surface, which allows the viewer to see rising or declining groundwater level changes. With the exception of wells installed more recently, the time axis for data presented starts in January 2005 and extends through the current period of measurement. A table is included listing the recorded water levels at each well being manually measure by DWR staff.
As the project was initiated in response to impacts of high groundwater levels, we have identified those wells where water levels are consistently within ten (10) feet of ground surface, and those wells where water levels are or have recently been within five (5) feet of ground surface:
|| Within 10 ft of Ground
||Within 5 ft of Ground|
| T5N, R65W
| T4N, R65W
||16-1, 48-2, 50-2, CSU WP166, 301-1
||DSS-19, DSS-20, DSS-21|
| T4N, R66W
||28-1, 34-1, 37-1, WL-M-003A
||18-1, 108-1, Lorenz, Greiman|
The 2015 water level readings in many wells with depths to water that are shallow (10 feet or less) have been at their highest levels since the project started. These wells also show an increasing trend over the past three years. The wells with historically high levels in 2015 include:
- CSU WP167, WL-M-401, WL-M-501, 15-1, 16-1, 39-1, 39-3, 300-1, 301-1, WL-M-009, DSS21BBD, 17-1, 18-1, 25-5, 27-1, 28-3, 30-1, 30-2, 32-1, 34-1, 36-1, 37-1, 37-4, 108-1, 208-9, CSU WP157, CSU WP162, WL-M-001, WL-M-003A, WL-M-006A, WL-M-007, and WL-M-008.
- Many of the hydrographs show a recent trend where winter/spring groundwater level lows have not declined to the previous year’s low. That is, the aquifer is not able to fully drain before it’s recharged again in spring/summer. This would also suggest that the higher groundwater levels haven’t produced a significant change in gradient from year to year, i.e. discharge to the river is not increasing with rising water levels as would be expected.
Certain areas within the Town of Gilcrest have noted higher than normal water levels in 2014 and 2015. Residents have noted water entering their basements and the town’s wastewater treatment facility has been impacted. As shown in the table above, wells 18-1; 108-1; Wl-M-003A; Lorenz; and Greiman to the east of the town report water levels within 5 feet of ground surface.
While both the spatial and temporal availability of water level data within the study is good, water levels were not recorded by Central in 2005 for most of their wells. As this time frame is central to stricter administration of well pumping and curtailment of many junior groundwater wells, we analyzed water level trends pre-2004 and post-2006. A map is presented that outlines an area (blue line) in which the ambient water levels in wells changed by 5 feet or more. In all cases, the post-2006 water levels were shallower than pre-2004 levels, but very few of these changes resulted in water levels approaching ground surface. To further illustrate this observation, a composite hydrograph is displayed for historic water level trends in wells in Township 4 north, Range 66 west from 1990 through 2016 to date.
The Colorado Geological Survey completed their work to refine the hydrogeology of the study area and analyze aquifer properties and flow directions. We have posted their entire report on the website. The Colorado Water Conservation Board recently contracted with the Colorado Geological Survey to update their water level analysis and mapping to include spring and fall of 2013 and 2014. Included herein are a groundwater elevation contour map for fall 2014, and a map showing depth to the water table for fall 2014 along with the fall 2013-14 changes. A large area directly east of the Town of Gilcrest is mapped as having water levels less than 5 feet from ground surface. Water level rises from 2 to almost 10 feet in an area approximately one mile north of the Town of Gilcrest are noted on their change map. This area corresponds with the Haren Recharge Facility.
Recently, the South Platte River basin groundwater technical subcommittee has been discussing potential mitigation measures to reduce high groundwater levels in the Town of Gilcrest. The final map shows monitoring well locations and their associated hydrographs for wells surrounding the town. The hydrographs are on a consistent vertical axis as depth below ground surface with a scale from zero to 32 feet. This allows for a comparison of depth to water by comparing the vertical position of the hydrograph on the y-axis. Many of these hydrographs show that water levels were at their historic highs, for the period graphed, during 2014. For example, well WL-M-006A experienced a 17 feet rise in water level between spring of 2013 and summer of 2014. The recent surface and near surface water levels reported from well WL-M-002 are the result of an instrument malfunction.
August 2016 Recharge Data
The LaSalle/Gilcrest study area contains a number of recharge ponds, seep, and diversion ditches. These structures are shown and labeled on the following map. Seepage from both the ponds and ditches influence groundwater recharge and thus groundwater levels. Alternately, seepage ditches act as drains and also influence groundwater levels.
Unfortunately, historic return flows (seepage) from ditches are not quantified by the water commissioner unless that seepage is specifically credited for recharge. Consequently, this data only provides a partial picture of the recharge component.
To provide some perspective for how the recharge components of these structures may relate to the groundwater level data, we have included graphs of:
1. The total flow being diverted at the headgates of the Evans No. 2, Farmers Independent, FIDCO Tail, Godfrey/Section No.3, Lower Latham, Union, and the Western/Hewes/Cook ditches. Since daily seepage values for these structures are not available, the total amount of water being diverted provides a qualitative assessment of both timing and amount of seepage. All of these ditches actively divert water from April through October. A summary, composite graph and individual charts for each ditch are provided on the same axis scale, 0-300 cfs. Also included is a bar graph illustrating annual ditch diversions since water year 2012.
2. The amount of water flowing into recharge ponds associated with the ditches within the study area. The recharge ponds are organized by the ditch system supplying water and presented from north to south or west to east depending upon the alignment of the ditch. The data provides the schedule or timing for when these recharge ponds were filling. We do not have data on the volume of water within the structure, but the actual flow rate provides an indication of the amount of water diverted to recharge. Graphs are created only for those ponds with recorded diversions.
a. The graphs for ponds on the Evans No. 2 have a uniform axis of 0-5 cfs. Many of the ponds associated with the Evans No.2 started diverting water for recharge as early as February 2016.
b. The graphs for the ponds associated with the Western Hewes Cook ditch use different ranges for the discharge axis. The Haren recharge facility started receiving water in March, while many of the other recharge ponds started diverting water in April.
c. Graphs associated with ponds on the Farmers Independent ditch are also plotted with different ranges for the discharge axis. Large spikes in the data are most likely due to data entry errors. Most ponds are diverting for recharge in the first quarter of 2015.
d. The Miller Feedlot pond is the only recharge structure diverting from the Union ditch within the study area. Water year 2014 data was not available for this structure. This recharge pond started diverting in April this year.
e. New to this update is a bar graph illustrating annual pond recharge diversions by ditch system since water year 2012. The Haren Recharge Area clearly dominates the recharge activity.
3. Finally, we produce some cumulative pond recharge graphs by source ditch. The Evans No. 2 and Union ditches graphs are plotted on a diversion axis range of 0-5,000 acre-feet, Farmers Independent ditch uses 0-10,000 acre-feet, and the Western Hewes Cook ditch uses 0-20,000 acre-feet. These graphs were produced to quickly identify those ditches and recharge structures that have the greatest impact on the system. The Farmers Independent and Western Hewes Cook ditches provide the vast majority of recharge water, with the Heron and former Farr recharge areas dominating. The Farr recharge pond has not diverted water since the 2014 water year. The quantity of water being placed in those structures may influence local water levels as a groundwater mound would be generated beneath the pond.
1. Sterling & Gilcrest LaSalle High Groundwater Analysis - Brown & Caldwell- Final Report
2. Colorado Geological Survey Hydrogeologic Characterization Report
3. Addendum to Gilcrest - LaSalle Pilot Project Hydrogeologic Characterization Report (2015)
1. Gilcrest / LaSalle Groundwater Investigation (September 9, 2014)
2. Presentation to South Platte Roundtable Groundwater Committee (July 9, 2013)
3. Initial Presentation (January 24, 2013)