Lanhai Li

Using path analysis to identify the influence of climatic factors on spring peak flow dominated by snowmelt in an alpine watershed

Spring snowmelt peak flow (SSPF) can cause serious damage. Precipitation as rainfall directly contributes to the SSPF and influences the characteristics of the SSPF, while temperature indirectly impacts the SSPF by shaping snowmelt rate and determining the soil frozen state which partitions snowmelt water into surface runoff and soil infiltration water in spring. It is necessary to identify the important and significant paths of climatic factors influencing the SSPF and provide estimates of the magnitude and significance of hypothesized causal connections between climatic factors and the SSPF. This study used path analysis with a selection of five factors — the antecedent precipitation index (API), spring precipitation (SP), winter precipitation as snowfall (WS), <0°C temperature accumulation in winter (|ATN|), and average >0°C temperature accumulation in spring (AT) — to analyze their influences on the SSPF in the Kaidu River in Xinjiang, China. The results show that |ATN|, AT and WS have a significant correlation with the SSPF, while API and SP do not show a significant correlation. AT and WS directly influence the SSPF, while as the influence of |ATN| on SSPF is indirect through WS and AT. The indirect influence of |ATN| on SSPF through WS accounts for 69% of the total influence of |ATN| on SSPF. Compared to the multiple linear regression method, path analysis provides additional valuable information, including influencing paths from independent variables to the dependent variable as well as direct and indirect impacts of external variables on the internal variable. This information can help improve the description of snow melt and spring runoff in hydrologic models as well as the planning and management of water resources.

A model for food nutrient dynamics of semi-intensive pond fish culture

Abstract A dynamic model was developed to explain food nutrient dynamics in a semi-intensive aquaculture pond and to determine food nutrient requirements for supplementary feeds for Nile tilapia. The model links food nutrient production with elementary nutrient dynamics and fish growth by including four sectors: food nutrients, fish growth, elementary nutrients, and dissolved oxygen. The model, developed by using stella ii software, simulated a field experiment that was designed to determine limiting nutritional factors for fish growth in fertilized ponds. Simulation results show that supplementary feeding compensates for natural food nutrient deficiencies. Results also reveal that protein supplements are necessary for increasing fish yields of fertilized ponds. Comparison of the data from simulation and observation indicates that the simulation values have a close correspondence with observed data, and the model is able to capture essential food nutrient dynamics in semi-intensive aquaculture ponds.

Effects of levofloxacin hydrochlordie on photosystem II activity and heterogeneity of Synechocystis sp.

Effects of LH on photosynthesis of Synechocystis sp. were investigated by a variety of in vivo chlorophyll fluorescence. O2 evolution and the photosystem II (PSII) activity were clearly inhibited by LH. Exposure to LH increased the proportion of PSIIbeta and this weakened the connectivity between PSII units and hindered excitation energy-transfer between PSII units. LH decreased the density of the active photosynthetic reaction centers, inhibited electron transport, and increased the dissipated energy flux per reaction center. The inhibitory effect of LH on Q(A)(-) reoxidation process could be divided into several stages. LH first inhibited the electron transfer from Q(A)(-) to Q(B) by weakening the connectivity between Q(A)(-) and Q(B), and PQ binding began taking part in Q(A)(-) reoxidation. At the second stage, the connectivity between Q(A)(-) and PQ pool was broken and inhibition on PQ binding occurred. At this stage, some Q(A)(-) began to be oxidized by S2(Q(A)Q(B))(-). Finally, when the connectivity between Q(A)(-) and Q(B) and PQ was completely broken, all Q(A)(-) was oxidized through charge recombination.

Dynamics model to simulate water and salt balance of Bosten Lake in Xinjiang, China

Bosten Lake, the largest inland freshwater lake in China, is similar to other lakes in arid regions in that it faces shrinkage of its area and a decrease in environmental quality due to climate change and anthropogenic pressures. A water and salt balance model, developed using system dynamics approach, was used to estimate potential contributions of natural and socio-economic factors to variations in the lake’s level and salinity. Calibration of the model provided new estimates of conversion coefficients for the actual evaporation and dissolved salt from the lake bed. The sensitivity analysis indicated that the lake’s level and average salinity have significant and high correlation with the water exchange rate and evaporation of surface water. Analysis showed that (1) increasing water exchange of the lake promoted a decreasing average salinity of the lake and an increasing water supply to the downstream area of the lake; (2) the average unproductive water lost was larger than half of the average surface water inflow; (3) enlarging the agricultural area in the Konqi River basin instead of the Kaidu River basin promoted a decrease in the lake’s salinity as well as a decrease in the total amount of salt in the lake. This study implies that increasingly efficient water management practices and greater conservation of water resources are required to save Bosten Lake and its ecosystem.

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, agricultural production and the population through modeling the decision-making process of the water exploration explicitly, 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 investigate 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 improving 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.

Agricultural impact on environment and counter measures in Rwanda

Rapid intensive agriculture often generates serious environmental concerns including soil erosion, water pollution and greenhouses gases. This paper assesses the impact of agriculture and its practices on environment in Rwanda from 1990 to 2012. Data provided by the World Bank were analyzed with Origin Pro 9 for statistical analysis. Also, a review on physical-chemical parameters and heavy metals of water resources home to or surrounded by cultivated mountains was adopted in this study. The results showed that agricultural records decreased from 1990 to 1994. However, after then, the short season cropland like cereals increased from 7.04 to 17.45%; roots and tubers increased from 13.17 to 21.69% in 1995 and 2012, respectively, whilst permanent cropland remained constant at 10.13%. As Rwandan soil is almost steep slope, this heavily exposes the soil to erosion, fertility loss and landslides as permanent crops to enhance fertility and erosion control are decreasing. Also, fertilizers increased from 2,149 to 27,748 tons, irrigation spaced from 4,000 to 10,000 ha which can be the reasons of rise of agricultural emissions. The reviewed studies estimated high concentration of the total nitrogen, total suspended solids, manganese, lead and iron exceeding the standards of the European Union and World Health Organization. From the above findings, it is suggested to regularly monitor water quality and promote its purification measures, to fertilize and irrigate timely and appropriately, expand areas under agroforestry and permanent crops, promote bench terraces practices for durable soil erosion control and water quality in Rwanda. Key words: Agriculture, environment, Rwanda, soil erosion, water pollution.

Sensitivity of runoff to climatic variability in the northern and southern slopes of the Middle Tianshan Mountains, China

Temperature and precipitation play an important role in the distribution of intra-annual runoff by influencing the timing and contribution of different water sources. In the northern and southern slopes of the Middle Tianshan Mountains in China, the water sources of rivers are similar; however, the proportion and dominance of water sources contributing to runoff are different. Using the Manas River watershed in the northern slope and the Kaidu River watershed in the southern slope of the Middle Tianshan Mountains as case studies, we investigated the changes in annual runoff under climate change. A modified hydrological model was used to simulate runoff in the Kaidu River and Manas River watersheds. The results indicated that runoff was sensitive to precipitation variation in the southern slope and to temperature variation in the northern slope of the Middle Tianshan Mountains. Variations in temperature and precipitation substantially influence annual and seasonal runoff. An increase in temperature did not influence the volume of spring runoff; but it resulted in earlier spring peaks with higher levels of peak flow. Damages caused by spring peak flow from both slopes of the Middle Tianshan Mountains should be given more attention in future studies.

Reconstruction of hydrometeorological time series and its uncertainties for the Kaidu River Basin using multiple data sources

This paper tried to reconstruct the time series (TS) of monthly average temperature (MAT), monthly accumulated precipitation (MAP), and monthly accumulated runoff (MAR) during 1901–1960 in the Kaidu River Basin using the Delta method and the three-layered feed forward neural network with backpropagation algorithm (TLBP-FFNN) model. Uncertainties in the reconstruction of hydrometeorological parameters were also discussed. Available monthly observed hydrometeorological data covering the period 1961–2000 from the Kaidu River Basin, the monthly observed meteorological data from three stations in Central Asia, monthly grid climatic data from the Climatic Research Unit (CRU), and Coupled Model Intercomparison Project Phase 3 (CMIP3) dataset covering the period 1901–2000 were used for the reconstruction. It was found that the Delta method performed very well for calibrated and verified MAT in the Kaidu River Basin based on the monthly observed meteorological data from Central Asia, the monthly grid climatic data from CRU, and the CMIP3 dataset from 1961 to 2000. Although calibration and verification of MAP did not perform as well as MAT, MAP at Bayinbuluke station, an alpine meteorological station, showed a satisfactory result based on the data from CRU and CMIP3, indicating that the Delta method can be applied to reconstruct MAT in the Kaidu River Basin on the basis of the selected three data sources and MAP in the mountain area based on CRU and CMIP3. MAR at Dashankou station, a hydrological gauge station on the verge of the Tianshan Mountains, from 1961 to 2000 was well calibrated and verified using the TLBP-FFNN model with structure (8,1,1) by taking MAT and MAP of four meteorological stations from observation; CRU and CMIP3 data, respectively, as inputs; and the model was expanded to reconstruct TS during 1901–1960. While the characteristics of annual periodicity were depicted well by the TS of MAT, MAP, and MAR reconstructed over the target stations during the period 1901–1960, different high frequency signals were captured also. The annual average temperature (AAT) show a significant increasing trend during the 20th century, but annual accumulated precipitation (AAP) and annual accumulated runoff (AAR) do not. Although some uncertainties exist in the hydrometeorological reconstruction, this work should provide a viable reference for studying long-term change of climate and water resources as well as risk assessment of flood and drought in the Kaidu River Basin, a region of fast economic development.

Water in Central Asia: an integrated assessment for science-based management

Central Asia contains one of the largest internal drainage basins in the world, and its continental location results in limited availability of both surface and groundwater. Since the twentieth century, water resources of the region have been exploited beyond sustainable levels. From small Mongolian headwater streams to the mighty Aral Sea, surface waters have been partially desiccated. Demands from the agricultural, energy and raw material sectors as well as population growth have not only increased water abstractions, but also left a diverse and strong pollution footprint on rivers, lakes and groundwater bodies. Such changes in water quantity and quality have not only led to a degradation of aquatic and riparian ecosystems, but also they have placed the region’s socioeconomic development at risk. Because of the complexity of Central Asia’s water problems, integrated assessment and management approaches are required. Despite some shortcomings in practical implementation, the widespread adoption of the Integrated Water Resources Management and water–food–energy nexus approaches may be keys to a more sustainable future. This thematic issue aims to provide documentation of the current state of scientific knowledge, ranging from hydrological research to water quality investigations, and offers an assessment of ecosystems and the services provided by them. Reviews and case studies on different management options conclude the thematic issue by providing insights into field-tested solutions for the region’s water challenges.

Water losses in arid and semi-arid zone: Evaporation, evapotranspiration and seepage

The primary purpose of this study was to assess water losses by evapotranspiration, evaporation and seepage in arid zone. Normally, evaporation and seepage are the main causes of water losses. For modeling water losses, a combination of Genetic Programming (GP), Penman-Monteith (PM) and Penman combination model for measurement of evapotranspiration, evaporation and seepage has been developed. The results were found to be varying depending on how the evaporation and seepage phenomena are modeled. These results show that that there is an improvement in reducing evapotranspiration, evaporation and seepage losses in arid and semi-arid region.