Formulating an Elasticity Approach to Quantify the Effects of Climate Variability and Ecological Restoration on Sediment Discharge Change in the Loess Plateau, China

Abstract

Suspended sediment yields (SSY) respond strongly to ecological restoration (ER) efforts, and significant improvements in SSY control have been achieved in the Loess Plateau of China. However, it remains challenging to quantify the net impacts of ER on SSY. Here, we formulate the notion of elasticity of sediment discharge, by associating SSY change to climate variability and ER over the period 1950s to 2014. All ten of the subcatchments studied experienced significant decreases in annual SSY, streamflow, and suspended sediment concentration. Our results strongly support the hypothesis that changes to both streamflow volumes and to the suspended sediment concentration versus water discharge (C‐Q) relationships result in reduced SSY, so that streamflow is reduced but runs clearer. We find that two of the ER strategies resulted in weaker relative impacts of climate variability, largely by reducing streamflow (by 55% to 75%). Meanwhile, ER predominantly decreased SSY (by 63% to 81%). Regarding ER practices, (i) the predominant measure acting to reduce SSY changed, over time, from engineering to reforestation; (ii) check dams preferentially act to regulate the C‐Q relationships, whereas reforestation preferentially acts to moderate streamflow. Overall, our results suggest that a combination of engineering and vegetation measures is critical to achieving high‐efficiency ER. While change to the ER strategy increased the efficiency of streamflow for SSY control, the lost water discharge per unit SSY reduction increased from 5.2 to 6.4 m3·t−1. Conflicting demands for water necessitate that further ER should target precision management by revegetation of targeted areas in the Loess Plateau.

Evaluation of Climate Change on Streamflow, Sediment, and Nutrient Load at Watershed Scale

“…Apart from that, water holding capacity of soil and landcover type also affect hydrology and water quality. The change in streamflow, sediment and nutrients are also influenced by human activities such as agricultural operation, construction, and mining [35]. The prediction of the future hydrological and water quality scenarios based on different climate scenarios input using two climate models developed in this study, will be useful in the development and implementation of effective watershed management mitigation strategies in the near and far future.…”

Complex relationships between water discharge and sediment concentration across the Loess Plateau, China

“…Their main function is to intercept sediment to create farmland. Check dams promote sediment deposition by intercepting and slowing the discharge (Liu et al, 2018), and thus alter the relationship between water discharge and sediment flux (Zhang et al, 2019). Li and Liu (2018) report that 50,935 check dams had been built in the upper reaches of the Yellow River, above Tongguan station (at the mainstream of the Yellow River) by 2012 when the average amount of intercepting sediment reached 204 million tons per year.…”

Changes of Flow and Sediment Transport in the Lower Min River in Southeastern China under the Impacts of Climate Variability and Human Activities

“…Generally, changes of suspended sediment load (SSL) can be attributed to climate variability and human activities. The elasticity approach proposed by [19] is adopted and reformulated to quantify the effects of climate variability and human activities on changes of suspended sediment discharge in different periods, which are identified with abrupt-change detection methods.…”

“…Because the amount of sediment transport (Q S ) is the multiplication of the concentration of sediment (C) and streamflow discharge (Q), changes in Q S can be expressed in an elasticity form as [19]:…”

“…Changes in SSL attributed to changes in precipitation (∆Q s,P ), potential evapotranspiration (∆Q s,E 0 ), and land surface (by changing streamflow, ∆Q s,m , and moderating C~Q relationships, ∆Q s,C ) can be, respectively, expressed as (Zhang et al 2019) [19]:…”