Imperial Valley Water Authority

Data


Well Readings Page


Agricultural Irrigation Use Page


Rain Gauge Readings Page

Operation of Rain Gauge and Groundwater Monitoring Networks for the Imperial Valley Water Authority: Year 14: September 2005-August 2006

Operation of Rain Gauge and Groundwater Monitoring Networks for the Imperial Valley Water Authority: Year 15: September 2006-August 2007

Data sheets, Forms and PDFs (Map, Strategy and Permitting Ordinance),

2010 Meeting Dates

Information

The Imperial Valley Water Authority was established in 1989 by referendum. It comprises
all of Mason County and four townships in Tazewell County. It operates under the Water Authorities Act
of 1951. The act gives the trustees various powers, one of which is 'To reasonably regulate the use
of water and during any period of actual or threatened shortage, to establish limits upon or
priorities as to the use of water.'

The year 2000 saw dramatic drops in the water levels in most of the 13 observation wells in
Mason and Tazell counties where rainfall was below average for the year. However, despite below
average rainfall in 2000, data collected by the Imperial Valley Water Authority suggest that
the number of gallons of water pumped for irrigation was down too, probably due to the timing
of the rainfall.

The long-term annual rainfall measured in the Imperial Valley Water Authority's Raingage
Network over the past seven years has been 35 to 37 inches. For the first 11 months of 2000
precipitation levels fell below that amount with an average of 27.60 inches among the 20 sites.

Interestingly, 8 to 12 inches of that amount came in the last ten days of June and the
first five days of July, representing nearly 40% of the year's total.

The Imperial Valley Water Authority also has a network of observation wells which have
been checked monthly since May 1995. These wells have shown a steady decline since the July-August
period of 1998. It appears the shortfall on precipitation translated into lower water levels.
Throughout most of 2000 the water in the wells was 2 to 3 1/2 feet lower than the same period
in 1999.

Not surprisingly, the only deviation was the June-July period, which was the only time
that rainfall was dramatically above average.

Using a formula based on power consumption a way has been determined to estimate the
amount of groundwater used by agricultural irrigation. For the irrigation season from June
to September it is estimated that 36.2 billion gallons were used in 2000 for irrigation. This
compares to 45.7 billion gallons in 1999, 35.9 billion gallons in 1998, and 45.3 billion
gallons in 1997.

Generally, July and August see the greatest average irrigation withdrawals. Although
2000 had below average rainfall, there was also below average irrigation use. What rainfall
there was came at the right time because only 60% of the total irrigation was used during
July-August, as compared to 70% in 1999, 74% in 1998 and 87% in 1997. Despit the shortfall
in rain, more water was pumped in five of the past six years than was pumped in 2000, even
though there are more systems in use today than ever before.

As we enter the new millennium, observers look at the historical data to seek out
expected trends for the future. Groundwater data going back to 1930 shows that in the first
part of each decade, the water table has been above the average depth below land surface,
and the last half of each decade has been below the average depth below land surface, with
the exception of the 1950s when the water levels remained below average form 1949 to 1961.

If the pattern holds, it could be expected that this coming year should begin a time
of average to above average rainfall for a few years.

(The Imperial Valley Water Authority board has contracted service with the Illinois
State Water Survey to set up and maintain a network of raingage and observation sites. It
is the strategy of the board to continue to gather information and work with the State
Water Survey to obtain analysis and understanding of the information gathered.)

Trustees

Jeff Smith
Chairman

3278 CR 1030E
Chandlerville IL 62627

Dorland W. Smith
Secretary
E-Mail dormsmit@fgi.net

Wayne Deppert
Treasurer
E-Mail depperts@dpc.net

Don Osborn Jr.
Trustee

Mark J McGrath
Attorney
FAX (309) 359-8918

E-Mail McGrath_PC@hotmail.com

Steve Wilson, w/ISWS
Advisor
E-Mail swilson@ses.uiuc.edu
2204 Griffith Dr
Champaign IL 61820

The observation Wells are located at the various sites as indicated on the map.
They are dedicated wells, used only for the purpose to monitor the water table. The wells are
measured on the first day of each month, except January and February. During the high usage
months of July and August, the wells are also measured on the fifeenth.

The data for the Observation Wells will be updated monthly, exept January and February.

The raingage Network Stations were designed, set up, and are maintained by the Illinois
State Water Survey under contract with Imperial Valley Water Authority.

Local obervers pervorm weekly raingage maintenance at 11 sites, while the other nine
raingages are serviced monthly by a local person trained and paid by the Illinois State Water
Survey. As needed, a Champaign-based scientist vists the network to perform maintenance and
repairs.

The map shows the locations of the sites, and the data table shows the amount of
precipitation collected on a monthly basis. Also the monthly average compared to the previous
year.

The estimated gallons withdrawn by agricultural irrigation is shown, and is compared with
several previous years. A formula was devised to determine the gallons used by irrigation. The
results of this formula compares favorably with the study conducted by the Illinois State Water
Survey in the years 1988 and 1989.

Imperial Valley Water Authority

Data

Information

Trustees

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Created 4-30-1997 by Robb Roper