Water Provision in Chaparral Landscapes: Water Quality and Water Quantity

Abstract

Rivers and streams in chaparral landscapes provide both direct and -indirect critical services to humans. Water provision services can be broadly parsed into five categories: improvement of extractive water supply, improvement of instream water supply, water damage mitigation (e.g., flood control), water-related cultural services such as recreation, and water associated supporting services, such as enhancement of aquatic species biodiversity. Each of these services is influenced by the quantity and quality of water, location, and timing of flow. Water quantity and quality in California's chaparral landscapes are affected by sequential flooding and drying, particularly in small seasonal streams, resulting from the highly - seasonal precipitation patterns in Mediterranean-type climate regions. Fire is also a key factor affecting water quality and quantity. In these systems, water quantity is limited and quality often degraded, especially during the dry season. This is further exaggerated by diversions and withdrawals for urban, agriculture, and industrial uses, while future climate change could be particularly severe in these highly seasonal climate regions. Arguably, streams and rivers in chaparral landscapes are among the most vulnerable ecosystems to human activities, and are regularly subjected to various influences that may have deleterious effects on surface waters, such as groundwater pumping, conversion of natural lands to agriculture, cattle grazing, waste disposal, and urban encroachment. Because of high human population and agricultural demands in southern California, water security is essential. Reservoirs and storage facilities help provide this, although these alter the natural hydrographs of streams and rivers. Key management priorities to protect water provision services include the reduction of contaminants, eutrophication, and alteration of biogeochemical processes to reduce nutrient loads, along with establishing water-quality goals and aiding watershed protection. To best retain water provision services supplied by chaparral landscapes, coordination and efficiency of management practices and interventions across land jurisdictions, property lines, and watershed boundaries must be improved.