MEMORANDUM
To: Rebecca Keenan, PE
City of Visalia
From: William F. Young, PE
Date: December 27, 2023
Subject: East Side Regional Park Irrigation Wells
Ground Water Levels
The City of Visalia (City) is proposing to construct the East Site Regional Park (ESRP) on a 270-acre parcel of agricultural land within the City limits. The ESRP is a master planned park designed as a multi- purpose facility that will increase the City’s groundwater recharge capabilities, promote habitat restoration, and provide outdoor recreational activities. The ESRP will have athletic/recreational fields constructed as depressed areas (basins) that will provide groundwater recharge opportunities. The complete ESRP is bounded by County Road 152 on the east, East Houston Ave/SR 216 on the north, the Big Creek Transmission Lines on the west, and East Mineral King Avenue (northerly frontage road to SR 198) on the south.
The ESRP parcel has three City owned wells that were previously used for orchard irrigation. The City is refurbishing two of these wells for park irrigation purposes. The wells are located close to Oakes Ditch as it runs centrally through the park. The wells are designated as Well #1, south of Oakes Ditch and west of County Road 152, Well #2, north of Oakes Ditch and 1,000 ft west of County Road 152, and Well #3, located south of Oakes Ditch and 1,200 feet west of County Road 152.
In May 2020 the City has Kaweah Pump perform pump tests on these wells. These pump tests showed that Well #1 was capable of pumping 585 gallons per minute (gpm) and the water level was 74 feet below the surface. Well #2 was capable of pumping 742 gpm and the water level was 79 feet below the surface. The depths were checked again in March 2023, Well #1 was recorded at 92 feet below the surface and Well #2 was recorded at 103 feet below the surface. There are some concerns over the decreasing groundwater levels and the capabilities of the pumps design to provide ESRP irrigation water.
The pumps were checked and determined to be adequate at the lower groundwater level.
The City has requested additional review of the groundwater levels and trends. Records show that the groundwater levels in the Visalia area have been decreasing. The figure below shows the trend of the groundwater level at a nearby well. Minimal rainfall years of 2014-2015 and 2020-2021 show a lower groundwater level due to the lower rainfall/recharge of the groundwater basin. The graph also shows a lowering trend of the groundwater level from 1989 to 2020.
Memorandum
City of Visalia Groundwater Trends
December 27, 2023
From 2001 to 2020 the groundwater lowering trend appears to have slowed, although still lowering. This period shows a lowering of approximately 10 feet over 19 years verses 65 feet over 12 years for the 1989-2001 period. There are two factors in the fluctuation of the groundwater level, rate of extraction and rate of infiltration. Development of the area with residential and commercial/industrial properties may increase the need for water. This water is supplied by the groundwater basin. Development usually also increases the rate of rainfall runoff resulting in less water infiltrating into the groundwater table. The primary reason for the decrease is minimal rainfall years that contribute to less water infiltration.
Determining the causes of the decrease in groundwater levels would require a much broader study and is not the focus of this technical memorandum.
Wells #1 and #2 are being refurbished for irrigation water to ESRP. These wells are approximately 150 feet deep. The information presented shows that these wells are approaching the limits of their uses without be drilled to a deeper depth. Based upon the information presented in this Technical Memorandum the average groundwater level will drop approximately 25 feet over the next 50 years.
When considering minimal rainfall years, the groundwater level could be 75-80 feet deeper than that or a total of 100 feet deeper than current elevations. It is our recommendation that these well be deepened a minimum of 150 feet to provide a service life of 50 years.
Memorandum
City of Visalia Groundwater Trends
December 27, 2023