Borrego Valley groundwater basin
Borrego Valley Groundwater Basin, located in the very southern region of California, is one of the driest basins in the state. With climate change predicted to have strong effects into foreseeable future, the region is viewed with a skepticism in the sustainable use of water at current rates of consumption. Both natural and man-made geographic divisions within this basin allow for a closer inspection of the various management techniques implemented throughout the years, and provide a basis for what may be pursued for an uncertain future. Borrego Valley is groundwater basin 7-24 with California's Colorado River hydrologic region. Geography of region The Borrego Valley Groundwater Basin is housed underneath the Borrego Valley, which lies in both San Diego and Imperial counties of southern California. It reaches from the San Ysidro Mountains in San Diego County, to the east, where it enters Imperial County. As of 2016, the California Department of Water Resources split this basin into two sub-basins, Borrego Springs and Ocotillo Wells. The total surface area of this basin is 150,000 acres (240 square miles), encompassing three aquifers throughout the valley. The natural landscape of this area consists mostly of shrublands, rocky outcrops and sediment, with sparse forested areas. The altitudes in this region ranges from 30 feet below sea level in the Lower Borrego Valley, and exceeds 4,500 ft above sea level in the San Ysidro Mountains. The average amount of precipitation gained in the Borrego Valley basin is usually less than 5 inches, and falls throughout the year, due to the climate being mostly the same year-round. It is mostly arid and dry, with a slightly cooler winter. The valley contains three aquifers: the upper, middle, and lower. The uppermost aquifer is made of alluvial, fan, playa and eolian deposits from the time between the Holocene and Pleistocene, and is up to 1,000 feet thick at the northern end of the basin. This layer provides the main source of water for the Borrego Valley. Beneath this layer lies the middle and lower aquifers, containing Pleistocene-age continental deposits such as consolidated sand, gravel, and boulders. The middle aquifer is thickest in the center of the valley, measuring 700 feet, while the lower aquifer reaches depths of 1800 feet in the southern portion. Borrego Springs Sub-Basin This region lies exclusively in San Diego County, with its northernmost edge in the Santa Rosa Mountains, and the San Felipe / Yaqui Ridge anticline and San Felipe fault in the south. At the western boundary, the San Ysidro Mountains provide the demarcation, while the eastern edge is defined by both the Coyote Creek and Superstition Mountain faultlines. Coyote Creek flows into the valley toward Borrego Sink, the prominent collection point for runoff, that sometimes overflows into the San Felipe Wash. Flow between the sub-basins is inhibited due to the immense alluvial sediments in Borrego Springs being cut off from the San Felipe Wash by the presence of large geologic structures. The effect had on each sub-basin is a reduced influence of groundwater