Impacts of Climate Variability and Land Use Alterations on Frequency Distributions of Terrestrial Runoff Loading to Coastal Waters in Southern California 1
Impacts of Climate Variability and Land Use Alterations on Frequency Distributions of Terrestrial Runoff Loading to Coastal Waters in Southern California 1
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气候变化和土地利用变化对南加州沿海水域陆地径流负荷频率分布的影响 1
DOI：
10.1111/j.1752-1688.2007.00138.x
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
J. Melack
中科院分区：
文献类型：
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作者：
R. Beighley;T. Dunne;J. Melack
摘要： 来自沿海流域的水、沉积物、溶解和颗粒化学物质以及细菌的输送影响到近岸海洋和河口水域。在南加州，沿海分水岭以离散的脉冲将水和相关的成分输送到近岸系统。为了更好地理解这些流域的脉动特性，模拟的径流事件的频率分布包括：(1)三种土地利用条件(1929年、1998年、2050年)；(2)三个时间周期(所有水年-2002年)，只有厄尔尼诺年(1992年、1993年、1995年、1998年)；只有非厄尔尼诺年；(3)三个地区(流域、高地和低地)。在流域尺度上，从1929年到2050年，由于局部化的城市化，平均事件径流量显著增加(>；200%)(0.41.3 cm)，这使得1929年的主要径流来源(占流域径流的78%)转移到2050年的沿海平面(占流域径流的51%)。降水和径流频率分布的年际气候变异性很强，厄尔尼诺年的平均降雨量和径流量分别比非厄尔尼诺年大66%和60%。结合城市化和气候变化，2050年的土地条件导致厄尔尼诺年产生大型径流事件(>；3.0 cm)的可能性是非厄尔尼诺年的五倍。结合事件径流的频率分布和区域养分输出关系，我们发现，在厄尔尼诺年，每5个事件中就有一个事件产生径流≥2.5 cm和近岸临时硝酸盐和磷酸盐浓度分别为12和1.4 μM，约为环境条件的5-10倍。
Abstract: The transport of water, sediment, dissolved and particulate chemicals, and bacteria from coastal watersheds affects the nearshore marine and estuarine waters. In southern California, coastal watersheds deliver water and associated constituents to the nearshore system in discrete pulses. To better understand the pulsed nature of these watersheds, frequency distributions of simulated runoff events are presented for: (1) three land use conditions (1929, 1998, 2050); (2) three time periods (all water years 1989‐2002), only El Nino years (1992, 1993, 1995, 1998); and only non‐El Nino years; and (3) three regions (watershed, uplands, and lowlands). At the watershed scale, there was a significant increase (>200%) in mean event runoff from 1929 to 2050 (0.4‐1.3 cm) due to localized urbanization, which shifted the dominant sources of runoff from the mountains in 1929 (78% of watershed runoff) to the coastal plane for 2050 conditions (51% of watershed runoff). Inter‐annual climate variability was strong in the rainfall and runoff frequency distributions, with mean event rainfall and runoff 66 and 60% larger in El Nino relative to non‐El Nino years. Combining urbanization and climate variability, 2050 land conditions resulted in El Nino years being five times more likely to produce large (>3.0 cm) runoff events relative to non‐El Nino years. Combining frequency distributions of event runoff with regional nutrient export relationships, we show that in El Nino years, one in five events produced runoff ≥2.5 cm and temporary nearshore nitrate and phosphate concentrations of 12 and 1.4 μM, respectively, or approximately 5‐10 times above ambient conditions.