Watershed Ecohydrological Processes in a Changing Environment: Opportunities and Challenges

The study evaluates the surface water quality of the Bach Dang river basin. During the rainy season, the temperature, pH, EC, BOD5, COD, coliforms, ammonium and phosphate values were 27–37 oC, 6.6–8.9, 300–2200 μS/cm, 5–25 mg/L, 5–26 mg/L, 0–3000 MPN/100mL, below 0.01 mg/L, and 0.02 mg/L, respective. During the rainy and dry seasons, Zn, Pb, Cr, As, Fe and Mn levels were below drinking water limits. In the rainy season, the water quality index varied from 76 to 91, signifying medium to excellent water quality. The most outstanding water quality sites were the QN12, QN18, and QN22. During the dry season, most areas had moderate to excellent (WQI values between 61 and 93), except for QN01, QN03, QN04, QN05, QN06, QN07, QN11, QN16, QN17, QN19, and QN23, where it dropped to moderate (61–73). The temperatures were greater and higher EC values in the southeast. The DO concentrations were higher in the northwest and southeast in both seasons. The southern and southeastern regions exhibited more excellent COD and BOD5 values than the western, southwest, north, and northeast regions. The ammonium concentrations were higher in the southeast. During the dry season, the phosphate levels exceeded the permissible limit in the west, southeast, east, and northeast. Coliforms were below acceptable in both seasons, with greater levels in the northwest and northeast during the dry season. In addition, the Zn and Pb are favorably associated with the As, Mn, ammonium and phosphate in the rainy season. The COD positively correlated with the coliforms and BOD5. In the dry season, the pH inversely correlated with the Pb and Fe positively. The ammonium correlated negatively with the DO and positively with the phosphates. The pH negatively connected with the alkalinity, while the As positively correlated with the BOD5 and COD.

Section: The Water Quality Index (Wqi)mentioning

confidence: 99%

Surface water quality assessment in the Bach Dang river basin, Vietnam: using water quality index and geographical information system methods

Nguyen,

Tran,

Tap Van

et al. 2023

“…Vegetation restoration methods will affect the micrometeorological and micro-topographic conditions of the soil, and further change the freeze-thaw conditions inside the soil, which in turn will impact the spatial and temporal distribution of the unfrozen water content of the soil (Lu et al 2021, Cao et al 2022.…”

Section: Seasonal Variation Characteristics Of Soil Unfrozen Water Co...mentioning

confidence: 99%

Study on spatiotemporal changes and influencing factors of frozen soil moisture during freeze-thaw period under different ecological construction measures in the loess plateau of China

Cheng,

Wu,

et al. 2023

The climatic conditions and soil characteristics of the Loess Plateau in China make it have a unique freeze–thaw process and the distribution of soil unfrozen water. In order to elucidate the spatio-temporal variation of soil unfrozen water during freeze–thaw period and its influencing factors under different ecological construction measures, The spatial and temporal variation of soil unfrozen moisture and its main influencing factors in five different ecological plots in the Loess Plateau during freeze–thaw period were studied by combining field monitoring and indoor calculation. The results showed that: (1) the spatiotemporal changes of unfrozen water content in soil were different under different vegetation restoration methods. The variation of unfrozen water content in fallow land was the largest at 20cm depth, while the variation in surface 10cm was the largest in the other four plots. (2) The average unfrozen water content of soil in the representative soil layer can be estimated more accurately, and the best representative soil layer in the five sample plots is concentrated in 20–30 cm. (3) During seasonal freeze–thaw period, the main controlling environmental factors of unfrozen water content are air temperature and surface temperature. The results can provide reference for soil protection and water resources management in northwest China, especially in the Loess Plateau.

“…However, the impacts such as natural hydrologic rhythm change have attracted a growing awareness due to these impoundments on instream environment (Yang et al 2019). Especially, the variation range of water flow is limited to a small range and the number of high-flow pulses decrease, which would artificially lead the natural environment tend to be monotonous (Luo et al 2021a, Cao et al 2022. Based on the previous research, the ecological flow is fundamental to sustaining the aquatic environment and affect the availability and function of river habitat (Naiman et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Balancing economic and ecological benefits for hydro-junction operation based on the ecological flow from the four major Chinese carps: a case study from Xinjiang River, China

Zhang

Zhang³

et al. 2023

The construction and utilization of the hydro-junctions would change the water flow and affect the hydrologic process required for the survival and reproduction of the aquatic organism in the river basin. To investigate the influence of the construction of the Jiepai (JP) and Bazizui hydro-junction (BZZ) on the hydrologic process in the Xinjiang River and coordinate the benefits between power generation and downstream ecological protection of the four major Chinese carps (FMCC), a one-dimensional hydrodynamic model is established to simulate the river hydrological regime of the spawning site before and after the construction of BZZ. Meanwhile, eleven ecological hydrologic parameters are used to evaluate the degree of hydrological changes for the spawning site caused by JP and BZZ, and four hydrological methods are applied to calculate the minimal and optimal ecological flows to satisfy the demands of FMCC. The multi-objective operation model combined with the non-dominated sorting genetic algorithm Ⅱ(NSGA-Ⅱ) is established to evaluate the relationship among the objective functions and design the ecological operation scheme of BZZ. The results indicate that the hydrologic changes in the spawning site has been moderately changed since the construction of the JP and would change more after the construction of BZZ. An obvious antagonistic relationship between electricity generating and ecological changes are presented in the simulation results, and the multiobjective operation model could clearly increase the comprehensive benefits under three typical years (dry, average, and abundant) by 20%, 19%, and 34% with the corresponding electricity generating lost by 4.9%, 3.5%, and 4.1%, respectively. This study is expected to provide scientific guidance to coordinate the restrictions and conflicts between economic and ecological benefits of hydro-junction operation in the lower reaches of the Xinjiang River.