Patterns and magnitude of flow alteration in California, USA
Patterns and magnitude of flow alteration in California, USA
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美国加利福尼亚州水流变化的模式和幅度
DOI：
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发表时间：
2018
期刊：
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通讯作者：
J. Howard
中科院分区：
文献类型：
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作者：
J. Zimmerman;D. Carlisle;J. May;Kirk R. Klausmeyer;T. Grantham;L. Brown;J. Howard
资金信息 S.D. Bechtel Jr. 基金会 摘要 1. 量化自然流态对于水资源管理和水生生态系统保护至关重要。了解人类活动改变流量的程度对于制定有效的保护策略至关重要。评估流量变化需要估计在没有人类影响以及当前土地利用和水管理下预期的流量。 2. 有多种技术可以预测溪流和河流的流量；然而，还没有一种方法能够用于预测大区域和大时期的自然流动条件。我们利用机器学习统计模型来预测 1950 年至 2015 年加利福尼亚州的自然月流量（不受水管理或人为土地利用影响的自然水流），并使用来自参考流量计的时间相关且固定的流域变量。然后使用这些模型来估计该州所有河流的平均、最大和最小月流量。 3. 我们将全州 540 个水流计测量的观测流量与同一地点的预期自然流量进行了比较，以量化过去 20 年（1996-2015 年）流量变化的类型、频率和幅度。如果观察到的流量指标（月平均值、年最大值、年最小值）落在建模流量估计的 80% 预测区间之外，则认为量具已更改。 4. 我们发现，加州 540 个流量计中的 95% 在过去 20 年中至少有 1 个月发生过流量变化，并且 11% 的流量计经常发生变化（记录的月份中超过三分之二有流量变化的证据）。全州的变化类型各不相同，在一年中的不同时间，流量要么枯竭，要么膨胀，或者两者兼而有之。大多数更改的计量表（68%）在这段时间内的月流量中都表现出消耗和通货膨胀。月平均流量的通货膨胀在夏季最为普遍，而月流量的枯竭在全年都很明显。 5. 流量变化的类型、频率和幅度因地区而异。北海岸和中部海岸 > 80% 的计量表存在流量损耗，南海岸和旧金山湾 > 80% 的计量表测量到流量膨胀，而在旧金山湾 > 80% 的计量表存在明显的流量损耗和膨胀。
Funding information S.D. Bechtel Jr. Foundation Abstract 1. Quantifying the natural flow regime is essential for management of water resources and conservation of aquatic ecosystems. Understanding the degree to which anthropogenic activities have altered flows is critical for developing effective conservation strategies. Assessing flow alteration requires estimates of flows expected in the absence of human influence and under current land use and water management. 2. There are several techniques to predict flows in streams and rivers; however, none have been applied to make predictions of natural flow conditions over large regions and time periods. We utilised machine learning statistical models to predict natural monthly flows (natural streamflows without the influence of water management or anthropogenic land use) in California from 1950 to 2015, using time-dependent and fixed watershed variables from reference stream gages. These models were then used to make estimates of mean, maximum and minimum monthly flows in all streams in the state. 3. We compared observed flows measured at 540 stream gages across the state with expected natural flows at the same locations, to quantify the type, frequency and magnitude of flow alteration over the past 20 years (1996–2015). A gage was considered altered if an observed flow metric (monthly mean, annual maximum, annual minimum) fell outside the 80% prediction interval of the modelled flow estimate. 4. We found that 95% of the 540 stream gages in California had at least 1 month of altered flows over the past 20 years, and 11% of gages were frequently altered (over two-thirds of the months recorded had evidence of altered flows). The type of alteration varied across the state with flows being either depleted, inflated or a mix of both at different times of the year. Most altered gages (68%) exhibited both depletion and inflation in monthly flows over the time period. Inflation of monthly mean flows was most prevalent during the summer months, while depletion of monthly flows was evident throughout the year. 5. Type, frequency and magnitude of flow alteration varied by region. Flow depletion was present at >80% of gages in the North Coast and Central Coast, flow inflation was measured at >80% of gages in the South Coast and San Francisco Bay and both depletion and inflation were evident at >80% of gages in the