Hydrological effects of dams and water diversions on rivers of Mediterranean-climate regions: examples from California

• Kondolf, Mathias ^[1] ; Batalla, Ramon J. ^[2]
  1. [1] University of California System

     University of California System

     Estados Unidos

     
  2. [2] Universitat de Lleida

     Universitat de Lleida

     Lérida, España

     
• Localización: Catchment dynamics and river processes: Mediterranean and other climate regions / coord. por Celso García García, Ramón J. Batalla Villanueva, 2005, ISBN 9780444520845, págs. 197-211
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Rivers in Mediterranean-climate and other semi-arid regions tend to be more heavily impounded and thus their hydrology more strongly affected than rivers in humid climates because demand for water is greater (to supply irrigated agriculture) and runoff is out-of-phase with demand. The impounded runoff index (ratio of reservoir capacity divided by mean annual runoff) is 0.8 on the Sacramento and 1.2 on the San Joaquin Rivers of California, much higher than rates: encountered in humid Atlantic climate regions. As a result of these high levels of impoundment, the overall magnitude and seasonal distribution of flows has changed substantially. Flood peaks tend to be reduced: the Q(2) declined on average 53 and 81% in the Sacramento and San Joaquin River basins, respectively. On many rivers, summer baseflows have increased to supply irrigation diversions downstream, creating a flatter hydrograph that no longer supports dynamic channel processes and the aquatic ecosystem that depends upon such channel dynamics. Vegetation has encroached in the formerly active channels of many rivers in response to reduced flood scour and sediment supply.