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Seaside Model Report October 26, 2007 Data Used 2.4 Groundwater Levels To calibrate the groundwater model, data on groundwater levels were compiled. CH2M/Hill (Terry Foreman, 2005, written communication) provided water level measurements representing 1952-2004. Table 2.3 lists the measurements actually used in developing the model, which includes those measurements made during 1995 and later, and Figure 2.2 identifies the well locations. The model development was based only on the later measurements because they were considered to be the most reliable. 2.5 Groundwater Pumping To specify the pumping rates to be assigned within the model, data on groundwater production was compiled. CH2M/Hill (Terry Forman, 2005, written communication) provided information on annual groundwater production from individual wells. The production from the California American Water Co., City of Seaside, County of Monterey, and private wells was provided for 1956-2002. The production from Marina Coast Water District wells was provided for 1993-2002. Table 2.4 lists the compiled production and identifies the well owners, and Figure 2.1 shows well locations. As shown on Figure 2.1, groundwater pumping outside the study areas by CH2M/Hill (2005) and Yates and others (2005) was incorporated into the model. 2.6 Groundwater Recharge 2.6.1 Prior Investigations To specify the natural and secondary recharge rates to be assigned within the model, prior estimates of recharge were compiled. Both CH2M/Hill (2005) and Yates and others (2005) estimated the recharge to the Seaside groundwater basin. To estimate precipitation recharge, they used similar approaches, and they obtained similar results. They both used a soil-water budget approach. The approach involved simulating the inflow and outflow to the vegetative root zone. The inflow to the root zone is the precipitation infiltration, and the outflows are evapotranspiration and deep percolation. CH2M/Hill (2005) used a monthly time step to simulate these processes, and Yates and others (2005) used a daily time step. To estimate the secondary recharge from landscape irrigation, septic tanks, leaking pipes, and other sources, CH2M/Hill (2205) and Yates and others (2005) based their estimates on different approaches and data but produced similar estimates. CH2M/Hill (2005) and Yates and others (2005) use slightly different study-area boundaries, and their respective recharge estimates differ in part due to that. The study area used by CH2M/Hill contains 12,600 acres, and the study area used by Yates and others contains 12,300 acres. Nevertheless, when the respective recharge rates are expressed in terms of the average rate per unit area, the separate recharge estimates are nearly identical. The average rate for CH2M/Hill is 0.35 ft/yr, and the average rate for Yates and Others is 0.32 ft/yr. However, the recharge rate estimated by CH2M/Hill (2005) was used in the model. 11
Seaside Model Report October 26, 2007 Data Used The natural recharge rates estimated by either CH2M/Hill (2005) or Yates and others (2005) are based on their estimates of the potential evapotranspiration within their respective study areas. Presumably, CH2M/Hill (2005) and Yates and others (2005) considered the dual effects of distance from Monterey Bay and altitude in characterizing the evapotranspiration over their study areas. Nevertheless, the region representing the groundwater model contains more coastal area and more higher-altitude area than within the CH2M/Hill (2005) or Yates and others (2005) study areas. These characteristics of the model area are counter balancing with respect to potential evapotranspiration. Therefore, the average natural recharge within the model area probably is similar to the average natural recharge estimated by either CH2M/Hill (2005) or Yates and others (2005). Likewise, the secondary recharge rates estimated by either CH2M/Hill (2005) or Yates and others (2005) is based on the extent of the urbanized area within their respective study areas. The region representing the groundwater model is larger, but the proportion of urbanized area is not greatly different than within the study area used by CH2M/Hill (2005) or Yates and others (2005). Therefore, the average secondary recharge within the model area probably is similar to the average secondary recharge estimated by either CH2M/Hill (2005) or Yates and others (2005). 2.6.2 Satellite-Image Analysis As preparation for 2005 trial on the Seaside basin adjudication, Timothy Durbin, Inc. (2005, written communication) evaluated the water-budget approach used by CH2M/Hill (2005) and Yates and others (2005). The approached used by them equates the precipitation recharge to the precipitation minus the evapotranspiration. Satellite imagery was analyzed by Durbin to estimate the consumptive use of the native vegetation, and a satellite analysis was used to evaluate the reasonableness of the prior recharge estimates. Satellite imagery for the Seaside groundwater basin was related to consumptive use through the NDVI (Normalized Difference Vegetation Index) index (Gates, 1980). This index in turn is related to reflectances measurements acquired in the red and nearinfrared spectral regions by the expression (Sellers, 1985; Myneni and others, 1995) NDVI ρ NIR R = (2.1) ρ NIR − ρ + ρ R where ρ R is the red reflectance and ρ NIR is the near-infrared reflectance. Work by Sellers (1985) and Myneni and others (1995) has shown the NDVI is related directly to the energy adsorption of plant canopies and hence to transpiration. By design, NDVI values range from +1 (when ρ R = 0 ) to -1 (when ρ NIR = 0 ). However, the NDVI calculated from a particular satellite image and for a particular 12
Page 1 and 2: GROUNDWATER FLOW AND TRANSPORT MODE
Page 3 and 4: Seaside Model Report October 26, 20
Page 15: Seaside Model Report October 26, 20
Page 39 and 40: Tables
Page 41 and 42: Table 2.2 Monitoring Wells Location
Page 43 and 44: Table 2.3 Merasured Groundwater Alt
Page 45 and 46: Table 2.4a California American Wate
Page 47 and 48: Table 2.4c Annual Pumping from Priv
Page 49 and 50: Table 2.6 ET Corresponding to 1993
Page 51 and 52: Table 3.2 Groundwater Budget for 20
Page 53 and 54: Table 4.2 Groundwater Budget for 20
Page 55 and 56: ® Monterey Bay Marina Seaside Mode
Page 57 and 58: ® Monterey Bay Reliz Fault Ord Ter
Page 59 and 60: NW Monterey Bay Coastline SE El Tor
Page 61 and 62: -700 ® Monterey Bay -600 -500 -120
Page 63 and 64: ® -300 Monterey Bay -75 -200 -100
Page 65 and 66: ® Monterey Bay Model Boundary DWR
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® -20 -10 Marina Monterey Bay 10 0
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® Marina Monterey Bay Seaside Seaw
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® Monterey Bay Marina X X X X X Se
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® Monterey Bay Model Boundary NDVI
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® Castroville Salinas North Monter
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® Figure 3.2 Finite-element Mesh
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NE SW Seaside Fault Relize Fault Or
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Δh Δh z t-1 Case of Small h z >z
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Well C A C B B A L Δz e Le be Elem
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0 -5 Specified Head (ft) et) -10 -1
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® Monterey Bay Figure 3.10b Initia
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® Monterey Bay Figure 3.11b Initia
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2.0 1.5 Weighted Computed Head (ft)
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® Monterey Bay Figure 3.13b Comput
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® Monterey Bay Figure 3.14b Comput
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® Monterey Bay Figure 4.1b Compute
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® Monterey Monterey Bay Bay Monter
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