Rialto Basin Groundwater
Management Plan Update
June, 2024
RBGC Technical
Advisory Committee
Contents
•Historical Rainfall, Production, Spring Groundwater Levels •Observations
•Pumping
•Management Plan
RBGC Technical Advisory Committee
Slide 2
920
940
960
980
1,000
1,020
1,040
0 5
10 15
20 25
30 35
40 1960
1962
1964
1966
1968
1970
1972
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
2014
2016
2018
2020
2022
AVERAGE ELEVATION (FT)
ANNUAL RAINFALL (IN)
Historical Average Annual Rainfall in Rialto Basin and Averages of Spring-High Water Level Elevations in Rialto Basin Index Wells
Average Rainfall Avg of Spring-High Water Levels
RBGC Technical Advisory Committee
Slide 3
969.7 ft
1960-2021 rainfall data collected from
Stations 2146, 2166, 2159, 2198, 2286
Rainfall data not available after 2006
from rain stations 2159, 2198, 2286
Missing rainfall data estimated from
nearby weather stations through linear
interpolation
2022/23 data from Stations:
Highland (251), UC Riverside (44),
Lake Arrowhead (192)
1,002.3 ft
920
940
960
980
1,000
1,020
1,040
0 5,000
10,000
15,000
20,000
25,000
1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 2017 2019 2021 2023
AVERAGE ELEVATION (FT)
TOTAL BASIN PRODUCTION (AF)
Historical Annual Rialto Basin Production and Averages of Spring-High Water Level Elevations in Rialto Basin Index Wells
Colton Rialto FUWC WVWD Avg of Spring-High Water Levels RBGC Technical Advisory Committee
Slide 4
2017-2020 production from
FWC 2020 UWMP
2022/23 annual production
is for Water Year
1,002.3 ft
969.7 ft
Observations
RBGC Technical Advisory Committee
Slide 5
• Groundwater levels did not recover in Spring 2023 or Spring 2024 despite two years with above average rainfall
• Average rainfall
• 1960-2023: 15 in
• 2015-2023: 14.61 in
• Avg. Rainfall in 2022: 17.3 in (above normal)
• Avg. Rainfall in 2023: 28.4 in (wet)
• Average pumping
• 1966-2023*: 10,337 AF
• 2015-2023*: 10,516 AF
• Pumping in 2022: 12,237 AF (40% reduction – 13,498 AF) • Pumping in 2023: 11,325 AF (41% reduction – 13,328 AF) • It appears it will take multiple wet years or an imported water supply to get the Rialto Basin above the minimum threshold and restore the ability to pump more water
* Missing pumping data for 2021
Pumping
RBGC Technical Advisory Committee
Slide 6
• Long-term average safe yield: 11,900 AF
• Pumping Rights
• Maximum Curtailment Reduction: 50%
Producer Annual Production Rights
Colton 2,395
FUWC 3,152
Rialto 2,943
WVWD 3,307
11,797
Producer Adjustable Rights Fixed Rights NML Adjusted Rights Total Rights Colton 3,010 890 0 3,900
FUWC 550 370 5,014 5,394
Rialto 2,846 1,520 0 4,366
WVWD 5,594 510 0 6,104
19,764
Management Plan
RBGC Technical Advisory Committee
Slide 7
•Current management follows the 1961 Decree