Lower Salinas Valley Hydrologic Models: Discretization Data (ver. 1.1, July 2023)

The Lower Salinas Valley Hydrologic Models’ discretization data includes a shapefile of the model domain and layers and a shapefile of the water balance subregions. The Lower Salinas Valley Hydrologic Models include a historical model, the Salinas Valley Integrated Hydrologic Model (SVIHM) and a reservoir operations model, the Salinas Valley Operational Model (SVOM). While the Lower Salinas Valley Hydrologic Models have different purposes, they have the same model extent and many of the same input datasets, including the discretization data included in this data release. The model domain for the Lower Salinas Valley Hydrologic Models includes the Salinas Valley groundwater basin and extends offshore to include offshore aquifers in order to represent potential seawater intrusion. The aquifer system is bounded by faults and depositional or formational boundaries; Some of these faults cut across some of the aquifer layers, these faults in the interior of the model domain are simulated as potential hydrologic flow barriers. The total active modeled area is 10,266 square miles. The model grid is uniform, where each grid cell is approximately 6.46 acres (530-by-530 ft). There are 976 rows, 567 columns, and 9 layers having a varying number of active cells in each layer. The 9 model layers correspond to locally defined hydrostratigraphic units that represent aquifer systems that are separated by regionally extensive confining units. These include the saturated portions of the younger and older alluvium that represent the shallow aquifer that is underlain by the Salinas Valley Aquitard. These units overlie the Pressure 180-Foot Aquifer and the Pressure 180/400-Foot Aquitard, which in turn overlies the Pressure 400-Foot Aquifer, the underlying deep aquitard, and the basement bedrock of the Monterey Formation. The geologic units that comprise the aquifers and confining units above the Monterey Formation include the recent Alluvium, Aromas Formation, Paso Robles Formation, and Purisima Formation. The top of the Lower Salinas Valley Hydrologic Models' is represented by the altitude of the land surface, but because hydrostratigraphic units are discontinuous across the study area, the uppermost active layer is a composite of model layers 1, 3, 5, 7, and 9. The following are brief descriptions of the layers: (1) the uppermost shallow Quaternary Alluvial aquifer, (2) the Salinas Valley Aquitard, (3 & 5) the Pressure 180-Foot Aquifer, (4 & 6) the 180/400-Foot Aquitard, (7) the Paso Robles Formation, (8) the Purisima Formation, and (9) the basement bedrock. Within the model domain, a mass balance is maintained for 31 segments of the landscape called water balance subregions (WBS). The delineation of the water balance subregions is based on the management areas of the Monterey County Zone 2C jurisdictional region offshore regions, and areas outside of the Zone 2C jurisdictional region that are inside the active model domain (MCWRA, 2015; MCWRA, 2018).