Zhixiang Lu

Simulation of hydrological processes of mountainous watersheds in inland river basins: taking the Heihe Mainstream River as an example

The hydrological processes of mountainous watersheds in inland river basins are complicated. It is absolutely significant to quantify mountainous runoff for social, economic and ecological purposes. This paper takes the mountainous watershed of the Heihe Mainstream River as a study area to simulate the hydrological processes of mountainous watersheds in inland river basins by using the soil and water assessment tool (SWAT) model. SWAT simulation results show that both the Nash-Sutcliffe efficiency and the determination coefficient values of the calibration period (January 1995 to December 2002) and validation period (January 2002 to December 2009) are higher than 0.90, and the percent bias is controlled within ±5%, indicating that the simulation results are satisfactory. According to the SWAT performance, we discussed the yearly and monthly variation trends of the mountainous runoff and the runoff components. The results show that from 1996 to 2009, an indistinctive rising trend was observed for the yearly mountainous runoff, which is mainly recharged by lateral flow, and followed by shallow groundwater runoff and surface runoff. The monthly variation demonstrates that the mountainous runoff decreases slightly from May to July, contrary to other months. The mountainous runoff is mainly recharged by shallow groundwater runoff in January, February, and from October to December, by surface runoff in March and April, and by lateral flow from May to September.

Improving methyl parathion hydrolase to enhance its chlorpyrifos-hydrolysing efficiency

Methyl parathion hydrolase (MPH) can degrade a wide range of organophosphorus compounds, but its efficiency in hydrolysing chlorpyrifos, one of the most popular pesticides applied for crop protection, is much lower than that in hydrolysing the preferred substrate methyl parathion. In this study, random mutagenesis was adopted to improve MPH to enhance its efficiency in hydrolysing the poorly hydrolysed substrate chlorpyrifos. Rapid screening of the improved MPH variants was carried out using Bacillus subtilis WB800 secretory expression system to investigate the distribution of improved MPH variants based on the size of clear haloes as a result of chlorpyrifos hydrolysis. Four improved MPH variants were isolated, and one variant K3, in particular, showed a 5‐fold increase in kcat value for chlorpyrifos hydrolysis. Furthermore, most of the MPH variants obtained in this study possessed enhanced thermostability and pH stability. The approaches adopted in this study could be extended to create other MPH variants with increased activity for hydrolysing other poorly hydrolysed substrates.

Hydrologic Responses to Land Use Change in the Loess Plateau: Case Study in the Upper Fenhe River Watershed

We applied an integrated approach to investigate the impacts of land use and land cover (LULC) changes on hydrology at different scales in the Loess Plateau of China. Hydrological modeling was conducted for the LULC maps from remote sensing images at two times in the Upper Fenhe River watershed using the SWAT model. The main LULC changes in this watershed from 1995 to 2010 were the transformation of farmland into forests, grassland, and built-up land. The simulation results showed that forested land contributed more than any other LULC class to water yield, but built-up land had most impact due to small initial loss and infiltration. At basin scale, a comparison of the simulated hydrological components of two LULC maps showed that there were slight increases in average annual potential evapotranspiration, actual evapotranspiration, and water yield, but soil water decreased, between the two intervals. In subbasins, obvious LULC changes did not have clear impacts on hydrology, and the impacts may be affected by precipitation conditions. By linking a hydrological model to remote sensing image analysis, our approach of quantifying the impacts of LULC changes on hydrology at different scales provide quantitative information for stakeholders in making decisions for land and water resource management.

Evaluation of groundwater sustainability based on groundwater age simulation in the Zhangye Basin of Heihe River watershed, northwestern China

Water resources, as the primary limiting factor, constrain the economic and social development in arid inland areas. The Zhangye Basin is a representative area of inland river basins, which is located in the middle parts of the Heihe River watershed, northwestern China. Facing with the huge water shortage, people exploited groundwater at a large scale in recent years. The reducing recharge from surface water and over-exploitation of groundwater led to the decline of groundwater levels and threatened the sustainability of water resources. This study constructed a conceptual and numerical groundwater flow model and calibrated the model based on the observed wells. A solute transport model was built using MT3DMS to calculate the groundwater age distribution in the Zhangye Basin. The simulated result shows that the youngest groundwater is distributed near the most upstream areas in the model domain, which is less than 1,000 a, older groundwater is distributed in deeper parts of the aquifer and near the discharge outlets, ranging from 6,000 a to over 20,000 a. Spatial variation of groundwater ages in the middle area indicates the recharge diversity between unconfined and confined aquifer. Groundwater age can serve as an indicator to evaluate groundwater’s renewal capacity and sustainability. The formation of groundwater resources in the lower stream area would spend 10,000 a or even more than 20,000 a, so exploitation of groundwater in these areas should be restrained.

Co-evolutionary dynamics of the human-environment system in the Heihe River basin in the past 2000 years

There is limited quantitative understanding of interactions between human and environmental systems over the millennial scale. We aim to reveal the co-evolutionary dynamics of the human-environment system in a river basin by simulating the water use and net primary production (NPP) allocation for human and environmental systems over the last 2000years in Heihe River basin (HRB) in northwest China. We partition the catchment total evapotranspiration (ET) into ET for human and environmental systems with a social-hydrological framework and estimate the NPP for human and environmental systems using the Box-Lieth model, then classify the co-evolutionary processes of the human-environment system into distinct phases using the rate of changes of NPP over time, and discover the trade-offs or synergies relationships between them based on the elasticity of change of the NPP for humans to the change of NPP for environment. The co-evolutionary dynamics of human-environment system in the HRB can be divided into four periods, including: Phase I (Han Dynasty-Yuan Dynasty): predevelopment characterized by nearly no trade-offs between human and environment; Phase II (Yuan Dynasty-RC): slow agricultural development: characterized by a small human win due to small trade-offs between human and environment; Phase III (RC-2000): rapid agricultural development: characterized by a large human win due to large trade-offs between human and environment, and Phase IV (2000-2010): a rebalance characterized by large human wins with a small-environment win due to synergies, although these occurred very occasionally. This study provides a quantitative approach to describe the co-evolution of the human-environment system from the perspective of trade-offs and synergies in the millennial scale for the first time. The relationships between humans and environment changed from trade-off to synergy with the implementation of the water reallocation scheme in 2000. These findings improve the understanding of how humans influence environmental systems and responses to environmental stresses.

THE EFFECT OF WATER RESOURCE STRATEGY ON THE TERMINAL LAKE OF HEIHE RIVER BASIN FROM 2000 TO 2012

Water resources are the most significant factor restricting the basins development. The East Juyan Lake is the terminal lake belongs to part of the lower reaches in Heihe river basin of arid western China.because of the water reduction, the area of oasis degraded rapidly, especially influence the terminal lake and many ecoenvironmental problems have emerged in the lower reaches of Heihe River baisn. For the sake of improving the eco-environment, and deterring the trend of further degradation of the terminal lake, the “water diversion” project in the Heihe River was carried out in 2000. In order to objectively evaluate the influence of water regulation on restoration in this region, in this paper, by means of field surveys and water statistics from local government, the response range of the lake and and the variation of natural vegetation around the east lake in the lower reaches were described since 2000, These results show that there are obvious effects of water regulation on the restoration terminal lake and that the eco-environment is experiencing a good change in the terminal lake of inland Heihe river basin.