Hydrogeology. Konza LTER Workshop 1 September 2007 Gwen Macpherson

Transcription

1 Hydrogeology Konza LTER Workshop 1 September 2007 Gwen Macpherson

2 What We ve Learned Water flux Aquifer-atmosphere link Stream-aquifer interactions Chemistry

3 Aquifer-Atmosphere Link up to 33% of evapotranspiration is groundwater supported Mill Creek: York JP et al., 2002, Putting aquifers into atmospheric simulation models: an example from the Mill Creek Watershed, northeastern Kansas: ADVANCES IN WATER RESOURCES 25 (2): Gutowski WJ et al., 2002, A coupled land-atmosphere simulation program (CLASP): calibration and validation: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 107 (D16): Art. No daily oscillation in groundwater-level occurs during extended dry periods in the growing season Konza Prairie: Kissing, K. R., and G. L. Macpherson, 2006, Short-term water-level fluctuations and long-term water-level decline at the Konza Prairie drought or vegetation?: GSA Abstracts with Programs 38 (1): A

4 Daily water-level fluctuations: during growing season AND no rainfall ~ 3 cm /29/05 12:00 7/4/05 12:00 7/9/05 12:00 7/14/05 12:00 7/19/05 12:00 7/24/05 12:00 7/29/05 12:00

5 Atmosphere-Aquifer Interactions Annual pattern Impact of lower annual precipitation timing shift

6 2006 high-resolution water-level elevation in one well aquifer recharge

7 Average monthly precipitation mm Month

8 Stream-Aquifer Interactions Response times Direction

9 Stream-Aquifer Responses, Types 1 & 2 Water Level (cm) Delayed aquifer response Precip (in.) Stream Discharge (ft3/s) No stream response Rapid stream response 3/7/04 3/6/04 3/5/04 3/4/04 3/3/04 3/2/04 3/1/04 2/29/04 2/28/04

10 Stream-Aquifer Response, Type Water Level (cm) Delayed aquifer response Precip (in.) Stream Discharge (ft3/s) /23/04 8/24/04 8/25/04 Downstream stream response after aquifer response

11 Stream-Aquifer Interactions the future Computer models (D. Steward?)

12 What We Have Learned Water flux Aquifer-atmosphere link Stream-aquifer interactions Chemistry Annual cycles Solute sources Nutrient export CO 2

13 Annual chemical cycles ph, standard units Limestone dissolving Dilution DDB ph Modeled ph Alkalinity Calcium Magnesium /15/98 8/15/98 12/15/98 4/16/99 8/16/99 12/16/99 4/16/ Difference from 6-98 measurement, mmol L-1

14 Solute sources Sr/ 86 Sr Soil carbonate from dust? y = 3E-06x Bedrock carbonate /Sr (L/mmol) endmembers Wood, 2001

15 Solute sources, cont. 40 B Boron δ 11 B Source A: low low grass phytoliths? B: intermed. high rain? C: high low bedrock? 3-5 Mor Error bars: ±5 per Kissing, Kim, 2005 KU summer undergraduate research award project δ 11 B, per mil C A /B, 1/ppm

16 Nutrient export Manhattan Air Temperature, C February 17, 2007 February 16, 2007 Snow Note--x-axis is not true. February 18, 2007 Rapid Snowmelt Event (RSE)

17 Feb. 18 groundwater sampling ~8:30 pm, Water level elevation WL elevation 18 GW Temperature BL temperature Air temperature inside well /10/07 12:00 2/15/07 12:00 2/20/07 12:00 Groundwater temperature 2/25/07 12:00 3/2/07 12:00 3/7/07 12:00 3/12/07 12:00 3/17/07 12:00 8 3/22/07 12:00 ~7:30 pm, Rapid Snowmelt Event, RSE

18 Rapid Snowmelt Event, RSE 6 K (AAS or IC) K (ICP-AES) K/Ca, molar N04d Stream 0.04 K, ppm K/Ca, molar 0 10/01/89 10/01/94 10/01/99 09/30/

19 Rapid Snowmelt Event, RSE 3 K (AAS or IC) K (ICP-AES) NO3-N N04d Stream 0.6 K, ppm NO3-N, ppm /1/89 10/1/94 10/1/99 9/30/04 10/1/09 Time

20 CO { Groundwater CO 2 increase: ~20% (2100 ppm) Atmospheric CO 2 increase: ~7% (23 ppm) -1.4 log P-CO 2, groundwater log P-CO 2, atmosphere Niwot Ridge CO (Tans and Conway, 2005) 10/1/90 10/1/92 10/1/94 10/1/96 10/1/98 10/1/00 10/1/02 10/1/04 10/1/

21 Planning for the future (cont d) Develop new initiatives for LTER VI - Grassland responses to chronic N enrichment - Chronosequence of sites for restoration studies - Bison and fire as drivers of spatial patterns and consumer responses; linkages across temporal and spatial scales - Potential changes in fire/grazing treatments (?) to promote new science while ensuring site integrity - Groundwater sequestration of grassland CO 2 Integration of LTER with other major bioscience initiatives (LTER Regional Science Initiative, NEON, KSU Ecological Genomics program)

22 Are grasslands using more CO 2 than we think?? NEE Other fluxes in unsaturated zone CO 2 production net CO 2 flux GSC Water flux

23 Hydrogeochemistry the future Will annual cycles change because of changing lengths of seasons? With less meteoric precipitation, will chemical weathering affect bedrock relatively more? With a drier climate, will dust imports become more important, restock the soils with easily weatherable solids? With change in flora (more C3 s? or more zerophytes??), will biogeochemical cycling change? Is there an atmosphere-groundwater CO 2 link, and will it cause faster chemical weathering?

24 Approaches Watershed-scale measurements: Soil CO 2 to groundwater -- quantify the flux Dust import--quantify the flux Trace element cycling--what is unique about grasslands? Cross-site comparisons toward a global assessment Experiments: Isotope-tagged CO 2 transport