Subsurface Storage and Recovery: Perspective on Climate Change & Sustainability of Groundwater Quantity & Quality in California

Transcription

1 Subsurface Storage and Recovery: Perspective on Climate Change & Sustainability of Groundwater Quantity & Quality in California Graham E. Fogg Hydrologic Sciences Graduate Program Dept. of Land, Air and Water Resources Dept. of Geology Univ. of CA, Davis California s Water Storage Problem, the Underworld, and the Body Graham E. Fogg Hydrologic Sciences Graduate Program Dept. of Land, Air and Water Resources Dept. of Geology Univ. of CA, Davis 1

2 Collaborators Jeff Mount Jan Fleckenstein (Univ. of Bayreuth) Rich Niswonger (USGS) Casey Meirovitz Jeannette Sager Wes Christensen Laura Roll Sven Frei (Univ. of Bayreuth) Gary Weissmann (Univ. of NM) Reed Maxwell (LLNL; CO School of Mines) Funding U.S. Fish and Wildlife Service CALFED The Nature Conservancy Regional Water Authority Prop 50 2

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4 California Water System 7! CA Climate Change Center (2006) 8! 4

5 CA Water Plan 2005 The CA Water Problem! 7 th largest economy in the world.! Produces 50% of nation s fruits & vegetables w/ irrigation.! Depends on snow-storage and historically well-timed snow-melt to satisfy demand.! This system cannot function properly as the snow pack diminishes due to warming. 5

6 Solutions?! Conventional wisdom build more surface storage.! Unconventional wisdom subsurface storage of excess winter flow.! Plenty of storage space, but infiltration too slow.! Is there a way of accelerating recharge of the coming glut of winter runoff? Available Central Valley Storage Volume!10 to 50 million ac-ft!ca s 4 largest reservoirs = 13 million ac-ft (Shasta, Oroville, Trinity, New Melones) 6

7 Sutter Bypass, Sutter Co., 1997 flood Case study - Cosumnes River, California September 2001 Juni /35 7

8 2006 River-Aquifer Interaction Basics Aquifer said to be disconnected from stream 8

9 Heterogeneity models (geostatistics) river-scale reach-scale N sand sandy loam sandy clay N 40 km 125 m 12/35 The Body 9

10 Graham E. Fogg, 2002! River model simulated water table Fleckenstein, J.H., Niswonger R.G., & Fogg, G.E., Ground Water,44(6), /35 10

11 River model simulated seepage R = realization Fleckenstein, J.H., Niswonger R.G., & Fogg, G.E., Ground Water,44(6), /35 Heterogeneity model hypothetical model hypothetical model Jan Fleckenstein & Sven Frei 15/35 11

12 11/13/08 Different hydrofacies models percentage of total exchange depth below river [m] perching preferential flow zones depth below river [m] river length [km] river length [km] Jan Fleckenstein, Sven Frei & Reed Maxwell 21/35 Hypothetical model simulated saturation cross-sections preferential flow area perched area 0 depth below channel [m] depth below channel [m] length across river [km] grey colors indicate hydraulic K: dark grey = low, ligth grey = high Jan Fleckenstein & Sven Frei length across river [km] = full saturation 24/35 12

13 Sutter Bypass, Sutter Co., 1997 flood Flooding and Groundwater Levels 13

14 No Floodplain Levee Floodplain w/ set-back levees 14

15 BASE PROFILE FALL! BASE PROFILE LOWSTAND! BASE PROFILE RISE! BASE PROFILE HIGHSTAND :! Graham E. Fogg, 2002! 15

16 Where Paleosols Channeled Out, Vertical Flow Enhanced Graham E. Fogg, 2002! Kings River Fan Sequence Stratigraphy & Hydrofacies [G. Weissmann] 16

17 Summary! The new timing of runoff will require different mechanisms for storing water.! Regional hydrofacies approach leads to insights regarding mechanisms of groundwater and surface water interaction.! Subsurface storage of a sufficient magnitude not feasible unless! we know the sweet spots and can implement local enhancements to infiltration & vadose zone management?! and we allow floodplains to function like floodplains?! What about water quality? 17

18 Age Distribution & Sustainability Groundwater age distributions for well B4-2 (screen depth: 35.1 m) 18

19 Groundwater quality sustainability is one of the major scientific and societal issues of our time...!!! 37! Most fresh groundwater resources are yr old, yet most anthropogenic contaminants <50-60 yr old.! Especially in western alluvial basins, Gulf Coast, Atlantic coastal plain, etc.! Not so much in shallow, glacio-fluvial outwash, moist climates? Groundwater ages (even from short screens) are generally highly mixed.! Molecular ages typically range greatly (e.g., yr) within a single sample.! In other words, in many systems there is significant potential for water quality to get much worse over the coming decades to centuries, depending on contaminant sources. In addition to models, limited monitoring data are consistent with the things could get a lot worse argument. 37! Monitoring Data 19

20 Long-Term Measurements? From Dubrovsky, et al. (1998) - USGS NAWQA City of Davis, CA Well Data, <135 m Depth Major confining layers present 20

21 Davis Arava Valley, Southern Israel Water table aquifer Confined aquifer 42! 21

22 paper on groundwater sustainability argues that declining groundwater quality due to saltwater intrusion and irrigation with wastewater is seriously threatening the future of water resources in Israel as well as the economic and social fabric that depend on those resources. 43! But! There Are Potential Water Quality Benefits to Winter Recharge in CV! Fundamental: if most of the recharge is relatively clean, groundwater quality is much more sustainable.! Currently, most of the recharge in the CV is from irrigation.! Assuming the excess winter flows can be managed to maintain good quality.! Managed, clean recharge could actually help groundwater quality sustainability in the CV. 22

23 Closing Thoughts! The time has come to start thinking of a higher vision of how the CV aquifer system could be managed and used.! Currently we are most limited by lack of knowledge of the anatomy and by lack of will to think outside the box concerning groundwater.! There are technical and research problems to greatly augmenting SSR:! Getting floodwaters safely in contact with sweet spots! Dealing with the problem of clogging due to suspended sediment in winter flows! Effects on water quality! None of these are insurmountable 23