The Province operates a network of 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 %|
Hydrograph Analysis - Observation Well 124
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 Ft. St John 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 124 is completed in a bedrock aquifer to a depth of 82.9m. The ground water level in the well ranged from a high of 18.5m below ground level during May 1972 to a low of 20.5m during December 1992. The hydrograph shows that ground water levels follow a somewhat regular seasonal pattern, with maximum ground water levels occurring during April to July and minimum ground water levels occurring during November to February.
The CPD curve and monthly
precipitation plot, show seasonal and year-to-year cycles. Seasonally, precipitation
peaked during the months of July to September and is lowest in March and April.
Long- term variation is marked by years of below average precipitation in 1977,
1978, 1981,1982, 1985, 1986 and between 1998 and 2000. Years of above average
precipitation were recorded between 1971 and 1974 and from 1993 to 1997.
The gross relationship between precipitation and ground water levels can be recognized. Ground water levels in this well responded to the long-term precipitation trends as outlined in the CPD curve.