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Climate Variability Controls on Unsaturated Water and Chemical Movement, High Plains Aquifer, USA

^a USGS, Denver, CO
^b Geology and Geological Engineering, Colorado School of Mines, Golden, CO
^c USGS, San Diego, CA
^d Environmental Science and Engineering, Colorado School of Mines, Golden, CO
^e Bureau of Economic Geology, Austin, TX. Use of trade names is for reference only and does not constitute endorsement by the U.S. Government

View larger version (43K): [in this window] [in a new window]   FIG. 1. Map showing the location and extent of the High Plains aquifer, unsaturated zone monitoring network sites, and selected groundwater level (GW), pumping, and meteorological (P) stations.

View larger version (68K): [in this window] [in a new window]   FIG. 2. Daily time series (2001–2006) of precipitation and total (matric plus gravimetric) potential for selected depths below land surface (bls) at (a) northern High Plains (NHP) irrigated site (UMA); (b) NHP irrigated site (GNT); NHP rangeland site (IMP); (d) southern High Plains (SHP) irrigated site (JRW); (e) SHP irrigated site (MPL); and (f) SHP rangeland site (MWR). Daily time series of precipitation are shown for meteorological stations (a) P-1; (b,c) P-2; (d,e) P-6; and (f) P-5.

View larger version (38K): [in this window] [in a new window]   FIG. 3. Demonstration of data-processing steps using (a) total monthly precipitation from meteorological station P-1. The original series is transformed into a (b) monthly cumulative departure (MCD) series and is fitted with a low-order, cubic polynomial fit. The resulting residuals are normalized by the historic mean and referred to as the normalized departure series (c). Note the different y-axes for (b) and (c).

View larger version (34K): [in this window] [in a new window]   FIG. 4. Comparison of quasi-steady state total-potentials profiles for selected days before infiltration event (black crosses) and during infiltration events (white circles) at northern High Plains (NHP) irrigated sites (a,b) and rangeland site (c), and southern High Plains (SHP) irrigated sites (d,e) and rangeland site (f). These profiles extend to the water table (note different y-axis scales) and represent only 2 d from the complete record of total-potential time series shown in Fig. 2.

View larger version (29K): [in this window] [in a new window]   FIG. 5. Volumetric water-content profiles beneath the southern High Plains (SHP) irrigated sites JRW and MPL (a,b) and rangeland site MWR (c) that were obtained using neutron moisture meter. These profiles indicate 2005 wetting event reached depths that verify measurements from heat dissipation probes (HDPs), especially between 3 and 11 m below land surface at MWR site (HDPs were not located between 3 and 11 m at MWR).

View larger version (45K): [in this window] [in a new window]   FIG. 6. Comparison of profiles for chloride and nitrate concentrations in the vadose zone at central High Plains (CHP) rangeland and southern High Plains (SHP) rangeland and irrigated sites, 2000 and 2005.

View larger version (41K): [in this window] [in a new window]   FIG. 7. Total annual precipitation (mm) at meteorological stations (a) P-1 (1900–2005) and (b) P-5 (1921–2005).

View larger version (29K): [in this window] [in a new window]   FIG. 8. Distribution of total monthly precipitation (mm) at meteorological stations (a) P-1 (1900–2005), highlighting monthly precipitation for 2003, and (b) P-5 (1921–2005), highlighting monthly precipitation for 2004.

View larger version (60K): [in this window] [in a new window]   FIG. 9. The reconstructed components for paired precipitation and groundwater-level sites for (a) Pacific Decadal Oscillation (PDO)-range cycles (10–25 yr) and (b) El Niño/Southern Oscillation (ENSO)-range cycles (2–6 yr) are compared with respective PDO (Mantua and Hare, 2002) and multivariate ENSO (Wolter and Timlin, 1993) indices, shown in gray.

View larger version (45K): [in this window] [in a new window]   FIG. 10. Reconstructed components (RCs) for precipitation time series; meteorological stations (a,b) P-1 (northern High Plains) and (c,d) P-5 (southern High Plains). (PDO, Pacific Decadal Oscillation; >PDO, cycles with periodicities greater than PDO; NAMS, North American Monsoon System; ENSO, El Niño/Southern Oscillation; ANN, annual climate variability.)