A system dynamics approach for water resources policy analysis in arid land:a model for Manas River Basin

The Manas River Basin in Xinjiang Uygur autonomous region, similar to other arid regions, is facing water constraints which challenge decision-makers as to how to rationally allocate the available water resources to meet the demands from industries and natural ecosystems. Policies which integrate the supply and demand are needed to address the water stress issues. An object-oriented system dynamics model was developed to capture the interrelationships between water availability and increasing water demands from the growth of industries, agri- cultural production and the population through modeling the decision-making process of the water exploration ex- plicitly, in which water stress is used as a major indicator. The model is composed of four sectors： 1 ） natural surface and groundwater resources; 2） water demand; 3） the water exploitation process, including the decision to build reservoirs, canals and pumps; 4） water stress to which political and social systems respond through increasing the supply, limiting the growth or improving the water use efficiency. The model was calibrated using data from 1949 to 2009 for population growth, irrigated land area, industry output, perceived water stress, groundwater resources availability and the drying-out process of Manas River; and simulations were carried out from 2010 to 2050 on an annual time step. The comparison of results from calibration and observation showed that the model corresponds to observed behavior, and the simulated values fit the observed data and trends accurately. Sensitivity analysis showed that the model is robust to changes in model parameters related to population growth, land reclamation, pumping capacity and capital contribution to industry development capacity. Six scenarios were designed to inves- tigate the effectiveness of policy options in the area of reservoir relocation, urban water recycling, water demand control and groundwater pumping control. The simulation runs demonstrated that the technical solutions for im- proving water availability and water use efficiency are not sustainable. Acknowledging the carrying capacity of water resources and eliminating a growth-orientated value system are crucial for the sustainability of the Manas River Basin.

Impact of climate factors on runoff in the Kaidu River watershed:path analysis of 50-year data

Runoff formation is a complex meteorological-hydrological process impacted by many factors,especially in the inland river basin.Based on the data of daily mean air temperature,precipitation and runoff during the period of 1958-2007 in the Kaidu River watershed,this paper analyzed the changes in air temperature,precipitation and runoff and revealed the direct and indirect impacts of daily air temperature and precipitation on daily runoff by path analysis.The results showed that mean temperature time series of the annual,summer and autumn had a significant fluctuant increase during the last 50 years（P 0.05）.Only winter precipitation increased significantly（P 0.05） with a rate of 1.337 mm/10a.The annual and winter runoff depthes in the last 50 years significantly increased with the rates of 7.11 mm/10a and 1.85 mm/10a,respectively.The driving function of both daily temperature and precipitation on daily runoff in annual and seasonal levels is significant in the Kaidu River watershed by correlation analysis.The result of path analysis showed that the positive effect of daily air temperature on daily runoff depth is much higher than that of daily precipitation in annual,spring,autumn and winter,however,the trend is opposite in summer.

Assessment of soil degradation and chemical compositions in Rwandan tea-growing areas

This study has focused on the processes of soil degradation and chemical element concentration in tea-growing regions of Rwanda,Africa.Soil degradation accelerated by erosion is caused not only by topography but also by human activities.This soil degradation involves both the physical loss and reduction in the amount of topsoil associated with nutrient decline.Soil samples were collected from eleven tropical zones in Rwanda and from variable depth within each collecting site.Of these,Samples from three locations in each zone were analyzed in the laboratory,with the result that the pH of all soil samples is shown to be less than 5（pH〈5） with a general average of 4.4.The elements such as iron（Fe）, copper（Cu）,manganese（Mn）,and zinc（Zn） are present in high concentration levels.In contrast calcium （Ca） and sodium（Na） are present at low-level concentrations and carbon（C） was found in minimal concentrations.In addition,elements derived from fertilizers,such as nitrogen（N）,phosphorous（P）,and potassium（K） which is also from minerals such as feldspar,are also present in low-level concentrations. The results indicate that the soil in certain Rwandan tea plantations is acidic and that this level of pH may help explain,in addition to natural factors,the deficiency of some elements such as Ca,Mg,P and N.The use of chemical fertilizers,land use system and the location of fields relative to household plots are also considered to help explain why tea plantation soils are typically degraded.

Impacts of Climate Change on Snow Avalanche Activity Along a Transportation Corridor in the Tianshan Mountains

Snow avalanches can repeatedly occur along the same track under diferent snowpack and meteorological conditions during the snow season in areas of snow avalanche activity.The snowfall,air temperature,and snow cover can change dramatically in a warming climate,causing signifcant changes in the snow avalanche risk.But how the risk of snow avalanche activity during the snow season will change under a warming climate remains an open question.Based on the observed meteorological and snowpack data from 1968 to 2021 and the snow avalanche activity data during the 2011–2021 snow seasons along a transportation corridor in the central Tianshan Mountains that has a typical continental snow climate,we analyzed the temporal distribution of the snow avalanche activity and the impacts of climate change on it.The results indicate that the frequency of the snow avalanche activity is characterized by a Gaussian bimodal distribution,resulting from interactions between the snowfall,air temperature,and snowpack evolution.In addition,the active period of wet snow avalanches triggered by temperature surges and high solar radiation has gradually moved forward from the second half to the frst half of March with climate warming.The frequency and size of snowfall-triggered snow avalanches showed only a slight and insignifcant increase.These fndings are important for rationally arranging snow avalanche relief resources to improve the risk management of snow avalanche disasters,and highlight the necessity to immediately design risk mitigation strategies and disaster risk policies to improve our adaptation to climate change.

The triggering mechanisms for different types of snow avalanches in the continental snow climate of the central Tianshan Mountains

Climate change and human activities have increased avalanche risks in alpine mountains.Therefore,strengthening the research on mitigating and controlling avalanche disasters is indispensable for sustainable socio-economic development in mountainous areas.Early avalanche warning is an essential means of avalanche disaster prevention.However,the theoretical development and application of avalanche warning strategies remain limited due to the lack of systematic understanding of the triggering mechanisms of avalanches.Based on observational data(2015–2019)of avalanches,snowpack,meteorological parameters,surface soil temperature and moisture,and topography in avalanche-prone areas in the central Tianshan Mountains,we analyzed the characteristics of different types of avalanches under a continental snow climate and the environmental factors(such as meteorological conditions and snowpack)that trigger avalanches,as well as the triggering mechanisms for different types of avalanches under the continental snow climate in terms of snow-layer shear fracture modes.We found that the snowpack parameters,weather conditions,and soil temperature and moisture varied significantly among the stages of snow accumulation,stabilization,and melting,resulting in different avalanches prevailing in different stages of snowpack evolution.Moreover,the snow-layer fractures were driven by single external factors or the combined multiple factors under the continental snow climate.Fifty-four percent of the avalanche events in the study area occurred during or after a snowfall,with 36%related to sudden increases in temperature.Then considering different triggering scenarios,snowpack evolution stages,and the coupling of intrinsic and extrinsic drivers of triggering snow-layer shear failure,we constructed five snow-layer shear fracture modes and twelve avalanche-triggering modes on mountain slopes under a continental snow climate.

Effect of biochar amendment on soil's retention capacity for estrogenic hormones from poultry manure treatment

Most animals, including humans, produce natural sex hormones such as estrogens: 17β-estradiol(E2) and estrone(E1). These compounds are able to disrupt the reproductive systems of living organisms at trace concentrations(ng·L^(–1)). This experiment tests the hypothesis that 1% slow pyrolysis biochar-amended sandy soil could retain significant amount of estrogens(E1, E2)from poultry manure in its second year of application. The experiment was conducted over 46 days and consisted of a series of lysimeters containing sandy soil with biocharamended topsoil. The application rate of poultry manure was kept at 2.47 kg·m^(–2). The biochar held a significant concentration of hormone during the first year of its application. However, in the following year(current study), there was no significant retention of hormones in the biochar-amended soil. During the first year after application, the biochar was fresh, so its pores were available for hydrophobic interactions and held significant concentration of hormones. As time passed there were several biotic and abiotic changes on the surface of the biochar so that after some physical fragmentation, pores on the surface were no longer available for hydrophobic interactions. The biochar started releasing dissolved organic carbon, which facilitated greater mobility of hormones from poultry manure down the soil profile.