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 002
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 Abbotsford 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 002 is completed in the unconfined, sand and gravel, Abbotsford-Sumas Aquifer. Since 1966 the ground water level in the well has ranged from a high of 8.7m below ground level to a low of 15.4m below ground level. The hydrograph indicates that maximum ground water levels for this well occur seasonally during January and February and that minimum ground water levels occur seasonally during October and November. The difference between maximum and minimum ground water levels in one season ranges from approximately two to five metres.
The CPD curve exhibits strong seasonal and year-to-year cycles. Seasonally, December and January are high precipitation months and July and August are low precipitation months. Long-term variation is marked by years of below average precipitation between 1976 and 1980, 1985 and 1988, and 1992 to 1994. Years of above average precipitation were recorded between 1981 and 1984, 1988 and 1991 and 1995 to 1999.
There is a good similarity between
the CPD curve and well hydrograph with both curves exhibiting annual cyclical
fluctuations in response to precipitation. A brief lag period is evident in
which the fluctuations in the CPD curve precede those of the well hydrograph
by about one month.