Analysis on the Variation of Hydro-Meteorological Variables in the Yongding River Mountain Area Driven by Multiple Factors

Abstract

In recent decades, strong human activities have not only brought about climate change including both global warming and shifts in the weather patterns but have also caused anomalous variations of hydrological elements in different basins all around the world. Studying the mechanisms and causes of these hydrological variations scientifically is the basis for the management of water resources and the implementation of ecological protection. Therefore, taking the Yongding River mountain area as a representative watershed in China, the changes of different observed and simulated hydro-meteorological variables and their possible causes are analyzed on an inter-annual scale based on ground based observations and remotely sensed data of hydrology, meteorology and underlying surface characteristics from 1956 to 2016. The results show that the annual natural runoff of Guanting hydrological station in the main stream of the Yongding River, Cetian hydrological station and Xiangshuibao hydrological station in the tributary of the Yongding River all have a significant decreasing trend and abrupt changes, and all the abrupt change points of the annual natural runoff series of the three hydrological stations appear in the early 1980s. On the inter-annual scale, the water balance model with double parameters is unable to effectively simulate the natural surface runoff after the abrupt change points. The annual average precipitation after the abrupt change points decreases by no more than 10%, compared with that before the abrupt change points. However, the precipitation from July to August, which is the main runoff-production period, decreases by more than 25%, besides the intra-annual temporal distribution of precipitation becoming uniform and a significant decrease in effective rainfall, which is the source of the runoff. Meanwhile, the NDVI in the basin show an increasing trend, while the groundwater level and land water storage decrease significantly. These factors do not lead only to the continuous reduction of the annual natural runoff in the Yongding River mountain area from 1956 to 2016, but also result in significant changes of the hydro-meteorological relationship in the basin.

Attribution analysis of the spatiotemporal variation in water balance in a typical semiarid basin in northern China

“…$$ For the attribution analysis, as UYRB is one of the most water deficient region in China, the water consumption of the middle and lower reaches of the UYRB (GT, XSB, CT and SXL) is strongly dependent on the groundwater overexploitation, with more than 60% of the total water consumption in downstream provided by groundwater (Niu et al, 2021). According to the Grace land water storage data, the water storage of UYRB decreased by 172.5 mm ($$$ \Delta S=-172.5 $$$) during 2002–2016 (Niu et al, 2021) which indicated the water storage cannot be considered as constant for the whole UYRB. Therefore, only five mountainous sub‐watersheds (CGBN, CGBD, ZJK, GS and GYT) where water storages were assumed stable during the study periods were selected for quantitatively attribution analysis.…”

“…$$ The relative contributions of climate change ($$$ {\varphi R}_{\mathrm{C}} $$$) and human activities ($$$ {\varphi R}_{\mathrm{H}} $$$) to runoff change can be calculated as follows: $$$$ \Delta {R}_{\mathrm{H}}={R}_{2,\mathrm{Simulated}}-{R}_2, $$$$ $$$$ \Delta {R}_{\mathrm{C}}=\Delta R-\Delta {R}_{\mathrm{H}}, $$$$ $$$$ \varphi {R}_{\mathrm{C}}=\frac{\Delta {R}_{\mathrm{C}}}{\Delta R}, $$$$ $$$$ \varphi {R}_{\mathrm{H}}=\frac{\Delta {R}_{\mathrm{H}}}{\Delta R}. $$$$ For the attribution analysis, as UYRB is one of the most water deficient region in China, the water consumption of the middle and lower reaches of the UYRB (GT, XSB, CT and SXL) is strongly dependent on the groundwater overexploitation, with more than 60% of the total water consumption in downstream provided by groundwater (Niu et al, 2021). According to the Grace land water storage data, the water storage of UYRB decreased by 172.5 mm ($$$ \Delta S=-172.5 $$$) during 2002–2016 (Niu et al, 2021) which indicated the water storage cannot be considered as constant for the whole UYRB.…”

“…For the attribution analysis, as UYRB is one of the most water deficient region in China, the water consumption of the middle and lower reaches of the UYRB (GT, XSB, CT and SXL) is strongly dependent on the groundwater overexploitation, with more than 60% of the total water consumption in downstream provided by groundwater (Niu et al, 2021). According to the Grace land water storage data, the water storage of UYRB decreased by 172.5 mm (ΔS ¼ À172:5) during…”

“…2002-2016 (Niu et al, 2021) which indicated the water storage cannot be considered as constant for the whole UYRB. Therefore, only five mountainous sub-watersheds (CGBN, CGBD, ZJK, GS and GYT)…”

Detection of climate transitions and discontinuities by Hurst rescaling

“…For example, the Budyko hypothesis (Budyko, 1948) has been used to analyse regional differences in long‐term annual water and energy balance time series to identify the influence of changes on mean annual runoff and evapotranspiration. Hurst rescaling can be used to examine how changes in streamflow can be explained by variability in precipitation and evapotranspiration (see Istanbulluoglu et al ., 2012; Niu et al ., 2021).…”