ABSTRACT1 . Strawberry Creek (37'52'N; 122O15'W) is the major focus of open space on the University of California, Berkeley (Alameda County, California, USA) campus; it provides visual amenity and variety, riparian and wildlife habitat, and educational and recreational opportunities. 2.Since the beginning of this century, urbanization of the catchment, channel alteration and water quality degradation combined to cause deterioration of the creek's habitat and overall environmental quality; this was manifested by a marked absence of flora and fauna, obvious water pollution and severe erosion. 3.In 1987 a restoration project was undertaken that focused on water-pollution and erosioncontrol measures. In 1989, native three-spined sticklebacks (Gasterosteus aculeatus) were successfully reintroduced. Family Biotic Index scores for the macroinvertebrate community indicated a change from the 'poor' water quality conditions in 1986 to 'good' water quality in 1991.4. Environmental education programmes now involve over 1500 students who use the creek each year in laboratory exercises; a popular natural history and conservation walking-tour guidebook has also been prepared. 5 . On-going restoration efforts include additional reintroductions of other native species, further environmental education efforts and monitoring.6. Obstacles and key factors that led to the successful implementation of this project are presented to assist in implementing similar ecological restoration projects of urban streams.

/ California's population increased 25% between 1980 and 1990, resulting in rapid and extensive urbanization. Of a total 123,000 ha urbanized in 42 of the state's 58 counties between 1984 and 1990, an estimated 13% occurred on irrigated prime farmland, and 48% on wildlands or fallow marginal farmlands. Sixty-six percent of all new irrigated farmland put into production between 1984 and 1990 was of lesser quality than the prime farmland taken out of production by urbanization. Factors dictating the agricultural development of marginal farmlands include the availability and price of water and land, agricultural commodity prices, and technical innovations such as drip irrigation systems that impact the feasibility and costs of production, The increasing amount of marginal farmland being put into production could have significant water quality consequences because marginal lands are generally steeper, have more erodible soils, poorer drainage, and require more fertilizer than prime farmlands. Although no data exist to test our hypothesis, and numerous variables preclude definitive predictions, the evidence suggests that new irrigated marginal lands can increase nonpoint source (NPS) pollution for a given size area by an order of magnitude in some cases.Large-scale land use conversion can have significant impacts on both surface water and groundwater quality. These impacts are especially well illustrated in California, where rapid population increase has resulted in conversion of prime agricultural land and undeveloped wildlands to urban uses. Less obvious but more importantly, many marginal lands have been placed into agricultural production with serious water quality implications because the marginal lands are typically more erodible and require greater fertilizer application than prime farmlands.In this study, we review the principal sources of water pollution in California, consider the probable long-term water quality impacts of land use conversion trends, and suggest possible water resource protection strategies.