Una zona regable la componen distintas unidades de riego conectadas hidrológicamente. Cuando las unidades de riego están organizadas en serie, una mejora de su ICUC (Coeficiente de Uso Consuntivo) tiene más impacto en el ICUC global que cuando las unidades de riego están en serie, pero la calidad del agua se degrada más. Si se conocen las relaciones hidráulicas entre las unidades de riego, el uso del agua en la zona regable puede analizarse a distintas escalas (desde la unidad de riego hasta la zona completa). En esta ponencia se incluye un caso estudio en California. Pudieron distinguirse zonas de más consumo hídrico, coincidiendo con una concentración de cultivos de alta demanda. La concentración de sales estimada fue mayor en el centro y el sur de la zona regable, donde el agua de riego pasa por varios ciclos de reuso y el suelo tiene mayor contenido de materia orgánica. A efectos de comparación, incluso una zona regable compleja puede reducirse a una zona equivalente supuestamente organizada en serie.

Una zona regable la componen distintas unidades de riego conectadas hidrologicamente. Cuando las unidades de riego estan organizadas en serie, una mejora de su ICUC (Coeficiente de Uso Consuntivo) tiene mas impacto en el ICUC global que cuando las unidades de riego estan en serie, pero la calidad del agua se degrada mas. Si se conocen las relaciones hidraulicas entre las unidades de riego, el uso del agua en la zona regable puede analizarse a distintas escalas (desde la unidad de riego hasta la zona completa). En esta ponencia se incluye un caso estudio en California. Pudieron distinguirse zonas de mas consumo hidrico, coincidiendo con una concentracion de cultivos de alta demanda. La concentracion de sales estimada fue mayor en el centro y el sur de la zona regable, donde el agua de riego pasa por varios ciclos de reuso y el suelo tiene mayor contenido de materia organica. A efectos de comparacion, incluso una zona regable compleja puede reducirse a una zona equivalente supuestamente organizada en serie.

This report has been prepared under contract to and fully funded by the Office of Biological Services of the U. S. Fish and Wildlife Service. The goals and purpose of this federal office are to review the impact on fish and wildlife resources of land, mineral and water development practices, such as offshore oil and gas exploration, development and production; construction of inshore pipeline canals and refineries; power plant construction/operation and urban development. This report, and five other southern California reports, covering Carpinteria Marsh (Santa Barbara County), Anaheim Bay-Huntington Harbor (Orange County), Mugu Lagoon (Ventura County), the Northern Santa Barbara County CoastalWetlands, and the Nipomo Dunes and Wetlands (San Luis Obispo County), are scheduled to be part of the Department's "Coastal Wetland Series" (see inside front cover). (154 pp.)

Tesis para optar a Magister Science de la Universidad de California en EUA, cuyo objetivo fundamental fue estudiar las relaciones entre la dinámica del crecimiento de las raíces y la disponibilidad de agua en el subsuelo en cultivos de maíz y sorgo de secano. En las parcelas sembradas con sorgo y maíz se determinó el contenido de humedad del suelo a diferentes profundidades y etapas de desarrollo de esos cultivos que crecieron entre 1970 y 1971. Este documento en ingles se halla estructurado con los siguientes capítulos: 1) Introducción; 2) Revisión de literatura; 3) Materiales y métodos; 4) Resultados y discusión; 5) Conclusiones y 6) Bibliografía consultada. (Resumen Julia Brito, 2009)

The Agua Tibia Mountains, located at the northern end of the Palomar Range, have historically been the site for very little botanical research when compared with other units of the Peninsular Ranges, such as the Santa Ana Mountains. This study reported the results of a floristic survey of the mountains that was conducted over a four-year period, from September 1994 through May 1999. This study area encompassed the drainage system of Agua Tibia Mountain and is topographically and geologically diverse. A complex mosaic of herbaceous, shrub- and tree-dominated vegetation was found in range. Vascular plant taxa reported for the mountains totaled 954, including 756 considered native and 198 considered nonnative. Among these were sensitive plant taxa. range extensions, and disjunct taxa that created a rich diversity of plant species and revealed important insights into the phytogeographic history of mountains.

High-frequency time series analysis and cross-correlation identified the relationship between precipitation and water-level responses at 16 sandstone wells in southern California, USA. The time series analysis suggested that the water table rises only when a threshold value of precipitation is reached during the rainy season that likely represents the water content deficit from the previous 7-month dry season being replenished before generating a water-table response. The cross-correlation indicates two statistically significant lag-times: 0–3 and 20–50 days. Confidence in these results was augmented by unprecedented and exceptionally high-resolution sampling frequency. Water pressure readings were collected every second and then analyzed to identify and remove the effects of barometric pressure changes, Earth tides and earthquakes on water levels. These effects are usually considered “noise” in recharge studies, but their accurate quantification helped assess the unconfined nature of the wells, minimize uncertainties of the results, and isolate the groundwater responses to precipitation. Diffusivity values for the thick unsaturated zone, based on the time lags, suggest quick responses are related to flow through fractures and longer time lags are associated with piston-type movement in the matrix. Fast responses were more likely for shallow water tables in response to high-intensity precipitation events and vice versa. These findings are consistent with those found, using lower resolution data, for the Chalk aquifer in England (UK), despite the contrasting fracture and matrix properties, hydrogeological setting and climatic conditions. Thus, the same style of response to precipitation is expected globally where similar fractured porous media are present.

As a result of pumping in excess of recharge, water levels in alluvial aquifers within the Eastern San Joaquin Groundwater Subbasin, 130 km east of San Francisco (California, USA), declined below sea level in the early 1950s and have remained so to the present. Chloride concentrations in some wells increased during that time and exceeded the US Environmental Protection Agency’s secondary maximum contaminant level of 250 mg/L, resulting in removal of some wells from service. Sources of high-chloride water include irrigation return in 16 % of sampled wells and water from delta sediments and deeper groundwater in 50 % of sampled wells. Chloride concentrations resulting from irrigation return commonly did not exceed 100 mg/L, although nitrate concentrations were as high as 25 mg/L as nitrogen. Chloride concentrations ranged from less than 100–2,050 mg/L in wells affected by water from delta sediments and deeper groundwater. Sequential electromagnetic logs show movement of high-chloride water from delta sediments to pumping wells through permeable interconnected aquifer layers. δD and δ¹⁸O data show most groundwater originated as recharge along the front of the Sierra Nevada, but tritium and carbon-14 data suggest recharge rates in this area are low and have decreased over recent geologic time. Managed aquifer recharge at two sites show differences in water-level responses to recharge and in the physical movement of recharged water with depth related to subsurface geology. Well-bore flow logs also show rapid movement of water from recharge sites through permeable interconnected aquifer layers to pumping wells.