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Conjunctive Use and Managed Recharge: Technical and Scientific Research Frontiers. A. T. Fisher 1 , C. Schmidt 2 , A. Racz 1 , M . Los Huertos 3 , B. Lockwood 4 , T. Russo 5 , S. Beganskas 1. 1 Earth and Planetary Sciences Department University of California, Santa Cruz

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conjunctive use and managed recharge technical and scientific research frontiers
Conjunctive Use and Managed Recharge:Technical and Scientific Research Frontiers

A. T. Fisher1, C. Schmidt2, A. Racz1, M. Los Huertos3, B. Lockwood4, T. Russo5, S. Beganskas1

1 Earth and Planetary Sciences Department

University of California, Santa Cruz

2 Department of Environmental Science

University of San Francisco

3 Division of Science and Environmental Policy,

California State University, Monterey Bay

4 Pajaro Valley Water Management Agency

5 Earth Institute, Columbia University

Climate Change and the

Future of Groundwater in California

CCWAS-IGERT

UC Davis

16 April 2014

groundwater recharge essential for sustaining water resources a hydrologic research frontier
Groundwater recharge: essential for sustaining water resources, a hydrologic research frontier
  • Groundwater recharge is:
  • Naturally occurring process
  • Primary input to most aquifers
  • Most difficult component of hydrologic cycle to measure
  • Managed Aquifer Recharge (MAR) is:
  • Increasingly important for groundwater management in CA
  • Feasible in many groundwater basins
  • Dependent on availability of appropriate supplies
  • Method to improve both water supply and water quality
  • A window into cryptic, subsurface processes (natural laboratory)
many forms of groundwater recharge natural managed
Many forms of groundwater recharge (natural, managed)

Regional Flow

  • Different recharge systems require specific conditions, design, operations – "all recharge is local"
slide4

Some Questions in Planning and Operating

Managed Recharge Projects

• Where are the best locations to enhance recharge?

• What will be the source of the water?

• What operational plan will provide the greatest benefit?

• How does recharge vary in space and time?

• What controls variability in recharge rates?

• What maintenance will be required for operating systems?

• What will be the impacts on water quality?

• What is the fate of recharged groundwater?

• What is the value of recharged water?

• Can recharge be monetized/incentivized?

• Who receives the benefits?

pajaro river and pajaro valley basins
Pajaro River and Pajaro Valley basins

PR basin: 3400 km2, multiple counties, tributaries, creeks

PV land use: urban, agricultural, rural

Surface water systems impaired by elevated nutrients and sediment (EPA)

Primary fresh water resource is groundwater

PV GW extraction exceeds the sustainable yield of the basin

overdraft is a regional challenge
Overdraft is a regional challenge

Pumping:

~55k ac-ft/yr

City of Watsonville:

~7k ac-ft/yr

Sustainable yield:

40k–45k (?) ac-ft/yr

(depends on pumping distribution, time horizon, natural variability)

Overdraft:

10k–15k (?) ac-ft/yr

(depends on definition, annual conditions, definitely large)

200 to 350 ft/yr

map from

PVWMA, 2012

weighting surface and subsurface data
Weighting Surface and Subsurface Data

Russo et al., 2014 – GW, in press

map of mar suitability
MAP of MAR Suitability

Harkin Slough MAR project

• Total area:

56,000 acres

• Upper quartile of SI (30-40): 7,200 acres (13%)

Harkins Slough MAR project (SI = 32)

High

MAR suitability

Low

Russo et al., 2014

modeling mar influence
Modeling MAR Influence

Coastal MAR

High MAR suitability

Russo et al., 2014

Variations in groundwater levels resulting from:

• Ten MAR projects, distributed randomly

• 4,000 ac-ft/yr additional MAR throughout basin

• 34 years of model operation (compare to basecase)

Coastal MAR gives faster benefit, at cost of "recovery efficiency"

installing infiltration testing system
Installing Infiltration Testing System

2. Build liner

1. Dig pit

4. Fully instrumented

3. Install thermal probes

infiltration test data stage versus time
Infiltration Test Data: Stage versus time

10 days

Stage (ft)

Stage (ft)

36 fill-empty cycles

24 hours

infiltration test data stage versus time1
Infiltration Test Data: Stage versus time

All data:

Final six minutes:

Long term infiltration capacity  20 ft/day

thermal probes used to determine vertical infiltration rate

∆

Thermal Probes Used to Determine Vertical Infiltration Rate

Pit

Shallow sediments

∆z

• Autonomous thermal probes in tubes at base of pit

• Diel temperature changes carried downward by infiltrating water

∆= Phase shift

Ar = Ad/As = Amplitude ratio

Racz et al., 2011

infiltration test data total and vertical infiltration
Infiltration Test Data: Total and vertical infiltration

All data:

Final six minutes:

Total infiltration : vertical infiltration = 10 : 1

Thermal data, ICVertical= 2 – 3 ft/day

slide18

Harkins Slough MAR project

• Up to 2000 ac-ft of water may be diverted from Harkins Slough to 7-acre recharge pond, infiltrated into shallow aquifer

• Water later recovered, blended with recycled water and other groundwater, distributed using coastal pipeline

slide19

view

Sampling and instrumentation

• Soil borings (grain size, carbon)

• Thermal and pressure probes (flow rates, soil properties)

• Piezometers and lysimeters (infiltration-fluid sampling)

• Monitoring wells (water levels, aquifer water sampling)

~7 acres

spatially variable and dynamic infiltration
Spatially variable and dynamic infiltration

Infiltration rate

15 January 2008

MAR day 5

modified from Racz et al. (2011)

spatially variable and dynamic infiltration1
Spatially variable and dynamic infiltration

Infiltration rate

30 January 2008

MAR day 20

modified from Racz et al. (2011)

spatially variable and dynamic infiltration2
Spatially variable and dynamic infiltration

Infiltration rate

14 February 2008

MAR day 35

modified from Racz et al. (2011)

spatially variable and dynamic infiltration3
Spatially variable and dynamic infiltration

Infiltration rate

29 February 2008

MAR day 50

modified from Racz et al. (2011)

spatially variable and dynamic infiltration4
Spatially variable and dynamic infiltration

Infiltration rate

14 March 2008

MAR day 65

modified from Racz et al. (2011)

spatially variable and dynamic infiltration5
Spatially variable and dynamic infiltration

Infiltration rate

29 March 2008

MAR day 80

modified from Racz et al. (2011)

slide26

Fluid sampling to assess changes in water quality as a function of infiltration rate, other parameters

Fluid sampling lines

Piezometers for

fluid sampling

Thermal monitoring tube

-0.5 m

-1.0 m

24–36 sample locations

C. Schmidt, USF

slide27

Nitrate concentration is reduced during infiltration

Profile

1

2

3

4

[NO3-] in pond

Nitrate

(μM)

Days of MAR, WY 2008

Schmidt et al. (2011a)

slide28

Nitrate load is reduced as well…

Pond

Profile 1

Profile 2

Profile 3

Profile 4

Load Reduction

Nitrate

Load

(kg N)

Load reduction of ~50%,

(600 kg of nitrate-N)

Days of MAR, WY 2008

…as a function of infiltration rate

Schmidt et al. (2011a)

thank you
Thank you!

Questions?

Reprints available: afisher@ucsc.edu

slide31

Some forms of groundwater recharge and management

Groundwater recharge

Natural recharge

Managed recharge

Regional

(precipitation)

Streambed

Irrigation

Surface

recharge (MAR)

Well

recharge

• Identify locations and quantify

• Protect and enhance

• Confined aquifer wells

• Water table wells

• Vadose zone wells

• Stream bank filtration

• Spreading basin/trench

Single purpose (injection)

or dual purpose (ASR)

• In-lieu recharge

• conjunctive use

central coastal ca is highly dependent on gw
Central coastal CA is highly dependent on GW

This provides challenges and opportunities for the

Pajaro Valley

GW = 83% of usage

DWR, Bulletin 160, 1998

ca spends a lot of money time and energy moving water across the state
CA spendsa lot of money,time, and energymoving wateracross the state.

Central coast hydrologic region is "lightly" involved in water transfers

dwr water plan update 160 98 status and projections for future needs
DWR Water Plan Update 160-98:status and projections for future needs

All units are Maf

Population (1995): 32.1 M

Population (2020): 47.5 M (+48%) estimated

dwr water plan update 160 09
DWR Water Plan Update 160-09:

Now includes environmental flows…

Much of this is overdraft

All units are Maf

• Climate change mentioned in 2005 update

slide37

San Francisco Bay Area

Precipitation stations

1890–2010

Years of record

120

15

Latitude (°N)

San Francisco

Stanford

50 km

Longitude (°W)

modified from Russo et al.(2013)

slide38

Compare 1890-1955 to 1956-2010:

Storm intensity has increased…

10 d

3 d

1 d

50

12

…likely reducing groundwater recharge

modified from Russo et al.(2013)

groundwater overdraft leads to numerous undesirable conditions and processes
Groundwater overdraft leads to numerous undesirable conditions and processes…

Overdraft can cause:

• seawater intrusion

• subsidence

• permanent loss of storage

• loss of stream or wetland flow

• development of dry gaps

• damage to riparian habitat

• lowering of water quality

some advantages of enhancing groundwater storage conjunctive use
Some advantages of enhancing groundwater storage/conjunctive use

• plenty of available space (another 5+ Mafeach year in CA!)

• less evaporative loss than surface storage

• may improve water quality (surface/ground)

• can be less impact on surface infrastructure

• can use less energy for storage and conveyance

• can use surface storage/conveyance multiple times

• can be cheaper than alternatives

• can respond to irregular supply, changing climate conditions

• can allow banking (increases flexibility)

• can be combined with LID, storm-water retention, other goals

• can improve aquatic habitat (lakes, streams, wetlands)

• can reduce seawater intrusion, other impacts from overdraft

• local solution to a local problem (can be politically viable)

slide41

Some challenges to enhancing groundwater storage/conjunctive use

• can require specialized infrastructure

• requires energy for construction and operation

• groundwater does not sit still, recovery <100%

• managed recharge comingles with ambient groundwater

• potential to harm water quality

• not all basins/partners have access to both suitable aquifers

• can lead to problems with infiltration, drainage

• stored water can't be seen

• water rights may be unclear; legal challenges likely

• permitting required for use of some water sources

• solving water supply challenges may promote growth

• local control can become regional control

• who goes first?