Groundwater Mound Study Discussions

The Central Nebraska Public Power and Irrigation District Groundwater Mound Study

Purpose ● Main Objectives  Evaluate the groundwater mound in the vicinity of lands irrigated by CNPPID facilities  Provide an understanding of the temporal and spatial changes of the groundwater mound  Identify factors affecting the groundwater mound

Key Terms ● CSD Groundwater Level Monitoring Reports  UNL-Conservation and Survey Division `

Key Terms ● CSD Wells  Database of water levels from wells used in CSD report

Key Terms ● Study Area

Groundwater Mound Study Recap ● Estimated Mound Volume  CSD well method  Water balance method ● Subareas ● Spatial and Temporal Movement ● Adjustment Impact  Diversions  ET

Groundwater Mound Size and Shape Annual Groundwater Mound Volume

Water Balance

Groundwater Evaluation

Water Balance

CSD Mound Volume Compared to Water Balance Mound Volume Mound Volume Calculated using the Water Balance

Mound Volume Calculated using CSD Well Data

Water Balance

Adjusted Diversions Annual Groundwater Mound Volume CSD Well Data 125% Diversions

75% Diversions 100% Diversions

50% Diversions

25% Diversions No Diversions

Water Balance

Adjusted ET Annual Groundwater Mound Volume

95% ET 98% ET 102% ET Un-Adjusted ET

105% ET CSD Well Data

Primary Conclusions ● Groundwater Mound Size and Volume  Increasing trend from the 1950s to 2000.  No longer an increasing trend since 2000.

The Future of the Mound ● Declining Surface Water Recharge  Reduced Water Supply in Lake McConaughy (Allocations)  Increased efficiencies (Conservation) • 1950-2000 average recharge = 145,000 af • Since 2000 average recharge = 90,000 af

● Declining Mound  Negative Water Balance

Canal Flow vs Precipitation 300000

20

18 250000 16

200000

Canal Flow, af

12

150000

10

8 100000 6

4 50000 2

0

0 1990

2002 Growing Season Precipitation

2012 Diversions

Deliveries

Growing Season Precipitation, inches

14

40

350,000.0

35

300,000.0

30

250,000.0

25

200,000.0

20

150,000.0

15

100,000.0

10

50,000.0

5

0.0

0

6 Month Rainfall

Canal Diversions, af

6 Month Rainfall, in

400,000.0

1942 1945 1948 1951 1954 1957 1960 1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 1999 2002 2005 2008 2011 2014

Irrigation Diversions, af

Irrigation Diversions vs 6 Month Rainfall

Historic Impact of a 25% Reduction of Diversions 5,000,000

4,500,000

Annual Groundwater Mound Volume (Acre Feet)

4,000,000

3,500,000

3,000,000

2,500,000

2,000,000

1,500,000

1,000,000

500,000

0

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

1991

1990

1989

1988

1987

1986

1985

Year CSD Mound Volume

Water Balance Mound Volume- Historic Diversions

Comparison of the water balance mound volume with adjusted diversion volumes.

Water Balance Mound Volume - 25% Diversion Reduction

2170

2165

2160

2155

Elevation (NGVD 29 MSL)

Declining Trend Matches Central’s Observation Well Data 2180

2175

2150

2145

Apr/2014 Apr/2013 Apr/2012 Apr/2011 Apr/2010 Apr/2009 Apr/2008 Apr/2007 Apr/2006 Apr/2005 Apr/2004 Apr/2003 Apr/2002 Apr/2001 Apr/2000 Apr/1999 Apr/1998 Apr/1997 Apr/1996 Apr/1995 Apr/1994 Apr/1993 Apr/1992 Apr/1991 Apr/1990 Apr/1989 Apr/1988 Apr/1987 Apr/1986 Apr/1985 Apr/1984 Apr/1983 Apr/1982 Apr/1981 Apr/1980 Apr/1979 Apr/1978 Apr/1977 Apr/1976 Apr/1975 Apr/1974 Apr/1973 Apr/1972 Apr/1971 Apr/1970 Apr/1969 Apr/1968 Apr/1967 Apr/1966 Apr/1965 Apr/1964 Apr/1963 Apr/1962 Apr/1961

Questions?