Static Groundwater Level Monitoring
The Little Blue NRD maintains an observation well network
to monitor the rises and declines of static groundwater levels. Static
level is the depth to water from ground surface while the aquifer is not
being influenced by pumping. There are 343 sites that are checked each
spring and fall by dropping a steel measuring tape down the space between
the well casing and pump column. The end of the tape is rubbed with
chalk, if the tape is dropped to 100 feet and the chalk is wet to two feet,
it is 98 feet to water in that well. The date is recorded and
the spring levels compared year to year. The District has been keeping
this data since 1975 and tracking long term trends of the static water
level.
Looking at the
township map first, the average water level
across the District rose +0.22 feet, the only Unit that fell was number 2.
In Unit 8 we measured 38 wells and they recorded an average rise of +0.63
feet. In Quantity Sub-Area 8, which lies within Unit 8, we measured 30
wells and they averaged only a small rise of +0.04 feet.
On the
2008 Spring Levels colored map, there was a
large area (in golds and yellows) to the north and east of Fairfield that
had lower levels. However; the data collected on water levels in the fall
of 2007 depicted a larger area of decline
across the District than this. Northern Thayer, Fillmore, and western Adams
counties are generally in light blue on the spring map, which represents a
rise of 0.00 to 2.00 feet. The water table in those areas, over the winter
months, rose more than the fall declines of 2007 indicated.
Interestingly;
townships 1 north and 3, 4 west; around and to either side of Chester,
didn’t hold to this pattern. The fall levels in this area were mixed, some
a little higher than the year before. But over the winter the numbers did
not come up enough to be higher in the spring of 2008, indicated by the
spotty areas of yellow and gold.
But ultimately, the
District’s Groundwater Management Plan looks at each well, and where its’
level is historically. Because of the lack of rainfall over the last
several years, in the spring of
2007 there were 156 wells that had dropped
below their “Action Level”, which is the lowest level on record for that
site. In the spring of
2008, even though there has been a modest
rise in the water table across the District, there are again 156 wells that
are lower than their Action Level. These weren’t the same wells, the water
table rises or falls across the District randomly, influenced by differing
rates of recharge or withdrawal.
Because it is an
isolated aquifer with special concerns as to quantity and quality; and
because of historical trends of declines, the District initiated a stay on
high capacity well drilling in Quantity Sub-Area 8. Across the rest of the
District, the action level is used as an indicator for need of heightened
concern. As outlined in the management plan, levels have not fallen (except
in Quantity Sub-Ares 8) to the point of requiring groundwater management
actions for quantity, as heard of in other areas of the state. And after
seven years of below average rainfall conditions; perhaps, as indicated by
this spring’s small rise, it is time for the water table to begin a turn
around of declining levels.
