The Ground Water Section of the Ministry operates a network of 163 observation wells to provide data on ground water level fluctuations and ground water quality information on developed aquifers in British Columbia. Observation well water levels are monitored using one of four methods: 1) manually with a wetted tape, 2) continuously using Steven's chart recorders, 3) electronically with data loggers or 4) remote monitoring using cellphone technology.
Water level data from observation wells are collected on a monthly basis by field observers and forwarded to Regional Offices. Data are then checked for errors and ommissions and forwarded to the Water and Air Monitoring and Reporting Section for final checking and storage. Water level data are referenced from ground level and the month end water level reading are entered and stored in Excel to produce a month-end hydrograph. The method of measurement and accuracy of each method are given below:
|Method of measurement||Accuracy|
|Wetted Tape Method||+/- 1 mm|
|Steven's Chart Recorder||+/- 1 mm|
|Data Logger||+/- 0.1 %|
The graphs above show the ground water level in the well (top), the cumulative precipitation departure or CPD (middle) and the actual monthly precipitation for the Castlegar Airport climate station (bottom). The CPD graph is a derivative of the precipitation data. The mean monthly precipitation over the study period is determined and the cumulative departures from the mean of the actual monthly amounts are plotted. CPD graphs can be useful in establishing how the ground water level in a particular aquifer responds to precipitation.
Observation well 074 is completed in an unmapped, unconfined, sand and gravel aquifer. The ground water level in the well ranged from a maximum of 19m below ground level during September 1999 to a minimum of 35.6m in October 1987. The ground water data is incomplete for portions of years 1980 to 1983 and 1995 to 2000. Despite gaps in the data, the hydrograph reveals that maximum ground water levels were reached during May, June and July and minimum ground water levels were reached during September and October.
The CPD curve is complex, and lacking obvious seasonal trends. Years of below average precipitation occurred between 1985 and 1994. Above average precipitation was recorded between 1980 and 1983 and from 1995 to 1998.
The hydrograph shows
seasonally erratic ground water levels likely caused by nearby pumping, causing
additional fluctuations of ground water levels and affecting the response of
ground water levels to precipitation. A gross relationship between precipitation
and ground water levels can be recognized only for the period 1996 to 2000.