Recent changes of water discharge and sediment load in the Yellow River basin, China

The Yellow River basin contributes approximately 6% of the sediment load from all river systems globally, and the annual runoff directly supports 12% of the Chinese population. As a result, describing and understanding recent variations of water discharge and sediment load under global change scenarios are of considerable importance. The present study considers the annual hydrologic series of the water discharge and sediment load of the Yellow River basin obtained from 15 gauging stations (10 mainstream, 5 tributaries). The Mann-Kendall test method was adopted to detect both gradual and abrupt change of hydrological series since the 1950s. With the exception of the area draining to the Upper Tangnaihai station, results indicate that both water discharge and sediment load have decreased significantly (p<0.05). The declining trend is greater with distance downstream, and drainage area has a significant positive effect on the rate of decline. It is suggested that the abrupt change of the water discharge from the late 1980s to the early 1990s arose from human extraction, and that the abrupt change in sediment load was linked to disturbance from reservoir construction.Geography, PhysicalGeosciences, MultidisciplinarySCI(E)43ARTICLE4541-5613

Sustainable Groundwater Management in the Arid Southwestern US: Coachella Valley, California

Sustainable groundwater management requires approaches to assess the influence of climate and management actions on the evolution of groundwater systems. Traditional approaches that apply continuity to assess groundwater sustainability fail to capture the spatial variability of aquifer responses. To address this gap, our study evaluates groundwater elevation data from the Coachella Valley, California, within a groundwater sustainability framework given the adoption of integrative management strategies in the valley. Our study details an innovative approach employing traditional statistical methods to improve understanding of aquifer responses. In this analysis, we evaluate trends at individual groundwater observation wells and regional groundwater behaviors using field significance. Regional elevation trends identified no significant trends during periods of intense groundwater replenishment, active since 1973, despite spatial variability in individual well trends. Our results illustrate the spatially limited effects of groundwater replenishment occur against a setting of long-term groundwater depletion, raising concerns over the definition of sustainable groundwater management in aquifer systems employing integrative management strategies

Increases in temperature do not translate to increased flooding.

In a recently published study and subsequent correspondence Yin et al.1,2 examine the sensitivity of precipitation and streamflow with temperature for the 99th percentile of precipitation and streamflow. The sensitivity of streamflow with temperature is found to be greater than the Clausius-Clapeyron (CC) relation of ~7% °C−1 and greater than the precipitation-temperature sensitivity. As a result, they conclude that storm runoff, in particular flash flooding, may increase (at more than the CC rate) in response to climate change. Although the authors state that similar studies have not been performed, an almost identical global study published over a year ago found largely contradictory results3. The Yin et al1 results oppose the prevailing tide of literature that suggests global streamflow extremes are more likely to be decreasing than increasing with climatic change4,5,6,7. Here we argue that the Yin et al1 results do not support the assertion that flash flooding will increase with climatic change, but rather are more likely to be related to changes in snowmelt processes