Salinity in the Colorado River Basin causes an estimated $300 to $400 million per year in economic damages in the United States. To inform and improve salinity‐control efforts, this study quantifies long‐term trends in salinity (dissolved solids) across the Upper Colorado River Basin (UCRB), including time periods prior to the construction of large dams and preceding the implementation of salinity‐control projects. Weighted Regressions on Time, Discharge, and Season was used with data sets of dissolved‐solids and specific‐conductance measurements, collected as early as 1929, to evaluate long‐term trends in dissolved‐solids loads and concentrations in streams from 1929 to 2019 (n = 14). Results indicate that large, widespread, and sustained downward trends in dissolved‐solids concentrations and loads occurred over the last 50–90 years. For 12 of the 14 stream sites with significant downward change, median declines of −38% (range of −14% to −57%) and −40% (range of −9 to −65%) were observed for flow‐normalized concentration and load, respectively. Steepest rates of decline occurred from 1980 to 2000, coincident with the initiation of salinity‐control efforts in the 1980s. However, there was a consistent slowing or reversing of downward trends after 2000 even though salinity‐control efforts continued. Significant decreases in salinity occurred as early as the 1940s at some streams, indicating that, in addition to salinity‐control projects, changes in land cover, land use, and/or climate substantially affect salinity transport in the UCRB. Observed dissolved‐solids trends are likely the result of changes to watershed‐related processes, not due to changes in the streamflow regime.

中文翻译：

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20世纪，1929–2019年，整个科罗拉多河上游流域的盐度大幅下降

科罗拉多河流域的盐度每年在美国造成300到4亿美元的经济损失。为了指导和改善盐度控制工作，本研究量化了整个科罗拉多河上游流域（UCRB）盐度（溶解固体）的长期趋势，包括在建造大坝之前和实施盐度控制之前的时间段。项目。将时间，流量和季节的加权回归与早在1929年收集的溶解固体和比电导率数据集一起使用，以评估1929年至2019年流中溶解固体负荷和浓度的长期趋势（ñ = 14）。结果表明，在过去的50-90年中，溶解固体的浓度和负荷出现了大的，广泛的和持续的下降趋势。对于14个流量显着向下变化的站点中的12个，流量归一化浓度的中值下降分别为-38％（范围为-14％至-57％）和-40％（范围为-9至-65％）。和负载。最严重的下降速度发生在1980年至2000年，与1980年代开始控制盐分的努力相吻合。但是，尽管盐碱控制工作仍在继续，但自2000年以来，下降趋势一直持续减缓或逆转。早在1940年代，一些河流的盐度就出现了显着下降，这表明，除了盐碱控制项目外，土地覆盖率，土地利用，和/或气候严重影响了UCRB中的盐分迁移。观察到的溶解固体趋势可能是与流域相关的过程变化的结果，而不是流径变化的结果。