Kairong Lin

Effect of Land Use and Climate Change on Runoff in the Dongjiang Basin of South China

Variability and availability of water resources under changing environment in a regional scale have been hot topics in recent years, due to the vulnerability of water resources associated with social and economic development. In this paper, four subbasins in the Dongjiang basin with a significant land use change were selected as case study. Runoffs of the four subbasins were simulated using the SCS monthly model to identify the quantitative impacts of land use and climate change. The results showed that (1), in the Dongjiang basin, temperature increased significantly, evaporation and sunlight decreased strongly, while precipitation showed a nonsignificant increase; (2) since the 1980s, land uses in the Dongjiang basin have experienced a significant change with a prominent increase in urban areas, a moderate increase in farmlands, and a great decrease in forest areas; (3) the SCS monthly model performed well in the four subbasins giving that the more significant land use change in each subbasin, the more runoff change correspondingly; (4) overall, runoff change was contributed half and half by climate change and human activities, respectively, in all the subbasins, in which about 20%~30% change was contributed by land use change.

A Two-stage Approach to Basin-scale Water Demand Prediction

Water demand prediction (WDP) is the basis for water allocation. However, traditional methods in WDP, such as statistical modeling, system dynamics modeling, and the water quota method have a critical disadvantage in that they do not consider any constraints, such as available water resources and ecological water demand. This study proposes a two-stage approach to basin-scale WDP under the constraints of total water use and ecological WD, aiming to flexibly respond to a dynamic environment. The prediction method was divided into two stages: (i) stage 1, which is the prediction of the constrained total WD of the whole basin (Tw) under the constraints of available water resources and total water use quota released by the local government and (ii) stage 2, which is the allocation of Tw to its subregions by applying game theory. The WD of each subregion (Ts) was predicted by calculating its weight based on selected indicators that cover regional socio-economic development and water use for different industries. The proposed approach was applied in the Dongjiang River (DjR) basin in South China. According to its constrained total water use quota and ecological WD, Tw data were 7.92, 7.3, and 5.96 billion m3 at the precipitation frequencies of 50%, 90%, and 95%, respectively (in stage 1). Industrial WDs in the domestic, primary, secondary, tertiary, and environment sectors are 1.08, 2.26, 2.02, 0.44, and 0.16 billion m3, respectively, in extreme dry years (in stage 2). Tw and Ts exhibit structures similar to that of observed water use, mainly in the upstream and midstream regions. A larger difference is observed between Ts and its total observed water use, owing to some uncertainties in calculating Tw. This study provides useful insights into adaptive basin-scale water allocation under climate change and the strict policy of water resource management.

Water allocation under the constraint of total water-use quota: a case from Dongjiang River Basin, South China

ABSTRACT A constrained total water-use policy has been implemented to maintain sustainable water supply in some water shortage areas. Managing a constrained water-use quota (T) in water allocation is a challenging goal. This paper proposes a new framework for water allocation under total water-use constraint by utilizing the concept of the Newsboy model, commonly used in operations management and applied economics, and applying it to the Dongjiang River Basin, South China. This framework considers T as a state variable of the objective function, rather than simply dealing with it as a constraint of multi-objective analysis. Using this framework, it is revealed how different schemes of T play out in water allocation, and water-use warning is provided for each sector and water governor in water resources management.

Fuzzy-Based Comprehensive Evaluation of Environmental Flow Alteration

Environmental flow alterations of the key factors influencing aquatic health of a river basin, and it is particularly true for highly-fragmented rivers. In this paper, a new comprehensive evaluation technique using the fuzzy theory was developed. The evaluation index system of environmental flow alteration was firstly established including the relative change of median and deviation, degree of alteration quantifies from range of variability approach (RVA), and histogram matching approach (HMA). Then, the weight of each evaluation index was determined using the entropy theory and order dualistic comparison method. Finally, the overall alteration degree of the 32 IHA (Indicators of Hydrologic Alteration) parameters was generated by fuzzy comprehensive method. Two main control stations, the Yichang station located at the outlet of the Upper Yangtze basin and the Gaoyao station located at the outlet of the west river of Pearl River basin, were selected as case study stations. The results showed that each evaluation index only reflects parts of characteristics of alteration in each parameter, and their contributions to comprehensive alteration of each IHA parameter were different over the stations. The developed comprehensive evaluation method can make the weight determination more scientific and credible, and effectively overcome the shortcomings of traditional single-factor evaluation and offer more reasonable quantitative evaluation of environmental flow alteration.

Quantifying the impacts of vegetation changes on catchment storage‐discharge dynamics using paired‐catchment data

It is widely recognized that vegetation changes can significantly affect the local water availability. Methods have been developed to predict the effects of vegetation change on water yield or total streamflow. However, it is still a challenge to predict changes in base flow following vegetation change due to limited understanding of catchment storage-discharge dynamics. In this study, the power law relationship for describing catchment storage-discharge dynamics is reformulated to quantify the changes in storage-discharge relationship resulting from vegetation changes using streamflow data from six paired-catchment experiments, of which two are deforestation catchments and four are afforestation catchments. Streamflow observations from the paired-catchment experiments clearly demonstrate that vegetation changes have led to significant changes in catchment storage-discharge relationships, accounting for about 83–128% of the changes in groundwater discharge in the treated catchments. Deforestation has led to increases in groundwater discharge (or base flow) but afforestation has resulted in decreases in groundwater discharge. Further analysis shows that the contribution of changes in groundwater discharge to the total changes in streamflow varies greatly among experimental catchments ranging from 12% to 80% with a mean of 38 ± 22% (μ ± σ). This study proposed a new method to quantify the effects of vegetation changes on groundwater discharge from catchment storage and will improve our predictability about the impacts of vegetation changes on catchment water yields.

Enhanced degradation of metronidazole by heterogeneous sono-Fenton reaction coupled ultrasound using Fe3O4 magnetic nanoparticles

Metronidazole (MNZ), one of the most commonly used nitroimidazole antibiotics in the world, poses a serious threat to human life and health. In this study, an enhanced sono-Fenton process for the degradation of MNZ is presented. The catalytic capacity of nano-Fe3O4 in systems comprising ultrasound + Fe3O4 + H2O2, and the influential parameters such as H2O2, nano-Fe3O4 doses and pH for the Sono-Fenton process, was investigated. The results showed that the nano-Fe3O4 particles appeared to be roughly spherical in shape, with an average size of 10-20 nm. It was found that •OH radicals were rapidly generated due to the catalytic activity of the nano-Fe3O4. MNZ could be degraded within a wide pH range, from 3 to 9, and the degradation efficiencies were considerably enhanced by ultrasound. When the MNZ concentration was fixed at 20 mg/L, the nano-Fe3O4 dosage at 500 mg/L, the pH at 3 and the reaction temperature at 30°C, the removal efficiencies of MNZ were above 98% after 5 h. It is indicated that Fe3O4 magnetic nanoparticles were synthesized as heterogeneous catalysts to effectively degrade MNZ, and the observed stability and recyclability demonstrated that nano-Fe3O4 was promising for the treatment of wastewater contaminated with antibiotics.

Considering the Order and Symmetry to Improve the Traditional RVA for Evaluation of Hydrologic Alteration of River Systems

Hydrologic alteration is one of the key factors influencing the aquatic health of a river basin, particularly that of highly fragmented rivers. In this study, we propose an improved range of variability approach (RVA) by considering the order and symmetry of indicators of hydrologic alteration (IHA) to comprehensively assess the hydrologic alteration of river flows. Three indices, i.e., index for the alteration of periodicity, index for the alteration of trend, and index for the alteration of symmetry, were used to improve the traditional RVA for evaluation of hydrologic alteration of river systems. Two main control stations located in the upper Pearl River Delta, the Sanshui and Makou stations, were selected as case studies. The results show that (1) each evaluation index reflects only partial characteristics of the alteration of each IHA parameter, which vary over the stations, and (2) the traditional RVA underestimates hydrologic alteration, because the trend and periodicity components and symmetry in the temporal order of IHAs were significantly altered, while the results of the traditional RVA varied slightly for some IHAs, e.g., the multiday maximum flow at the Sanshui station and monthly flows for May, July, and September at the Makou station. These indicated that, by considering frequency, trend, periodicity, and symmetry, the improved RVA provides a more accurate quantitative evaluation of ecological flow alteration.