Evaluation of the adaptability and response of indigenous trees to assisted rehabilitation on the degraded hillsides of Kuriftu Lake Catchment(Debre Zeit,Ethiopia)

Removal of trees and shrubs from hillsides exposes a site to erosion that threatens soil aggregation and stability. The present study aimed at evaluating the performance of five indigenous tree species in rehabilitation of degraded hillsides of Kuriftu Lake Catchment and the role of water harvesting structures. Adaptability varied by tree species and water harvesting structures significantly augmented seedling es-tablishment for some tree species. Height ofAcacia abyssinicaplanted on steeper slopes （18%-27%） without infiltration pits was lower than for conspecifics planted with infiltration pits.Dodonaea angustifolia wasproved to be best adapted to the siteand showed no need for water harvesting regardless of planting position across the degraded hillside. Planting ofAcacia seyalshould be restricted to gentler slopes （0-17%） with infiltration pits： tree height declined significantly on steep slopes without infiltration pits.Olea africanaperformed better on gentle slopes with pits but also grew well on steeper slopes with pits.Euclea schim-periwasproved to be least effective of the species evaluated in this study.

Evaluation of Agricultural Practices Scenarios for Reducing Erosion in Buyo Lake Catchment (Sassandra;Cote d’Ivoire) by Use of GIS

This study has used RUSLE model factors within a GIS component to evaluate eroded soil and developed viable agricultural practices scenarios to reduce soil loss in Buyo Lake catchment in the Western region of Côte d’Ivoire. Consequently, five study cases were tested as following: scenario 1—association of dense forest and crops with a high percentage of mulch;scenario 2—corn and sorghum combination by considering a high yield without conventional tillage;scenario 3—establishment of an herbaceous meadow;and scenario 4—association of palm, coffee, and cocoa with green cover. Scenario P was the setting up of straw mulch after corn or sorghum harvest. The erosion map resulting from these study cases showed by estimation, an average of soil loss of about 95 t/ha/year. The respective values obtained for the scenarios 1, 2 and 3 are 28 t/ha/year, 66 t/ha/year and 30 t/ha/year. This indicates a decrease of 68%. By scenario 4, the estimated average was 2 t/ha/year corresponding to a decrease of 98%. The combination of scenario 2 with scenario P gave soil losses average of 5 t/ha/year, i.e. a 95% reduction. This study shows that the association of palm, coffee, and cocoa with green cover would be very effective in reducing soil loss.

Determining soil redistribution in Dian Lake catchment by combined use of caesium-137 and selected chemical properties

Recent development in the use of the environmental radionuclide caesium-137 for documenting rates and soil redistribution on the cultivated or uncultivated land and estimating rates of sediment deposition on represents an important advance that overcomes many of the limitations of the conventional techniques commonly applied in such investigations. A study on soil redistribution （including soil erosion and deposition） was carried out in the Dian Lake catchment, Yunnan Province, using ^137Cs and selected chemical properties. The average soil erosion rate was 1,280.2 t km^2 yr^-1. Soil erosion rate occurring on different parts of the slope was significantly different on different parts of the slope, increasing.from the top. the bottom to the middle slope. The average soil erosion rate is also different with the land use type and that of the cultivated land （1, 672. 8 t km^-2 yr^-1） is higher than oJ the uncultivated land （1.161.2t km^-2 yr^-1 ）. The result shows that landform, slope gradient and land use type are key factors that influence the size of soil erosion. In addition, we also find the SOC and TN contents and amount of the soil erosion to be correlated in the soil. With the soil erosion occurring, there are land degradation and the local eco-environmental problems, such as water eutrophication in Dian Lake.

Simulation of denitrification in groundwater from Chaohu Lake Catchment,China

The eutrophication of Chaohu Lake in China is mainly attributed to nitrate inflow from non-point sources in the lake catchment. In this study,biological nitrate reduction from groundwater in the Chaohu Lake Catchment was investigated under laboratory conditions in a continuous upflow reactor. Sodium acetate served as the carbon source and electron donor. Results showed that a carbon-to-nitrogen(C/N) molar ratio of 3:1 and hydraulic retention time(HRT) of 8 d could achieve the most rapid nitrate nitrogen(NO_3^--N) depletion(from 100 mg/L to 1 mg/L within120 h). This rate was confirmed when field groundwater was tested in the reactor, in which a NO_3^--N removal rate of 97.71% was achieved(from60.35 mg/L to 1.38 mg/L within 120 h). Different levels of the initial NO_3^--N concentration(30, 50, 70, and 100 mg/L) showed observable influence on the denitrification rates, with an overall average NO_3^--N removal efficiency of 98.25% at 120 h. Nitrite nitrogen(NO_2^--N)accumulated in the initial 12 h, and then kept decreasing, until it reached 0.0254 mg/L at 120 h. Compared with the initial value, there was a slight accumulation of 0.04 mg/L for the ammonia nitrogen(NH4-N) concentration in the effluent, which is, however, less than the limit value.These results can provide a reference for evaluating performance of denitrification in situ.

Mapping of Potential Groundwater Recharge Zones in the Kolleru Lake Catchment, India, by Using Remote Sensing and GIS Techniques

Water scarcity is the major problem in India where the population has been tremendously increasing, which results in invading natural resources, thus affects on hydrological processes. Because of this, significant surface water bodies have been disappearing continuously. Therefore, more pressure on groundwater resources is a consequence of that. The integration of remote sensing and geographical information system (GIS), which helps in groundwater research for the investigation of potential groundwater availability, is essential to assess, monitor, and conserve groundwater resources. This analysis reports on the mapping of various potential groundwater resources in the Kolleru Lake catchment, India, by using remote sensing and GIS techniques. For this, a survey of India toposheets and IRC-1C satellite imageries was used to prepare thematic layers of geomorphology, drainage density, lineament, slope, land-use, soil, rainfall, and NDVI converted into raster format in ArcGIS. The raster maps of these thematic layers were assigned to a weight-based factor depending on the catchment characteristics and its topographic influence. The results demonstrated that about 7% of the area is under excellent groundwater potential recharge. Good, moderate, and lower potential conditions are 42%, 38%, and 13%, respectively. The results indicated that the management of groundwater potential zones should be targeted on the middle-catchment region. Further, the results were validated with the borehole data obtained from the Government of Andhra Pradesh-Groundwater Department. These results are useful for better both planning and groundwater management sources in the Kolleru Lake catchment.

Role of rural solid waste management in non-point source pollution control of Dianchi Lake catchments, China

In recent years,with control of the main muni-cipal and industrial point pollution sources and imple-mentation of cleaning for some inner pollution sources in the water body,the discharge of point source pollution decreased gradually,while non-point source pollution has become increasingly distressing in Dianchi Lake catch-ments.As one of the major targets in non-point source pollution control,an integrated solid waste controlling strategy combined with a technological solution and man-agement system was proposed and implemented based on the waste disposal situation and characteristics of rural solid waste in the demonstration area.As the key techno-logy in rural solid waste treatment,both centralized plant-scale composting and a dispersed farmer-operated waste treating system showed promise in rendering timely ben-efits in efficiency,large handling capacity,high quality of the end product,as well as good economic return.Problems encountered during multi-substrates co-com-posting such as pathogens,high moisture content,asyn-chronism in the decomposition of different substrates,and low quality of the end product can all be tackled.92.5% of solid waste was collected in the demonstration area,while the treating and recycling ratio reached 87.9%,which pre-vented 32.2 t nitrogen and 3.9 t phosphorus per year from entering the water body of Dianchi Lake after imple-mentation of the project.

The response of lake-glacier variations to climate change in Nam Co Catchment, central Tibetan Plateau, during 1970-2000

Based upon the 1970 aero-photo topographic map, and TM/ETM satellite images taken in 1991 and 2000, the authors artificially interpreted boundaries of lake and glaciers in Nam Co Catchment, and quantified lake-glacier area variations in different stages by ＂integrated method＂ with the support of GIS. Results show that from 1970 to 2000, lake area increased from 1942.34 km^2 to 1979.79 km^2 at a rate of 1.27 km^2/a, while glacier area decreased from 167.62 km^2 to 141.88 km^2 at a rate of 0.86 km^2/a. The increasing rate of lake in 1991-2000 was 1.76 km^2/a that was faster than 1.03 km^2/a in 1970-1991, while in the same period of time, the shrinking rates of glaciers were 0.97 km^2/a and 0.80 km^2/a respectively. Important factors, relevant to lake and glacier response to the climate, such as air temperature, precipitation, potential evapotranspiration and their values in warm and cold seasons, were discussed. The result suggests that temperature increasing is the main reason for the accelerated melting of glaciers. Lake expansion is mainly induced by the increase of the glacier melting water, increase of precipitation and obvious decrease of potential evapotranspiration. Precipitation, evaporation and their linkages with lake enlargement on regional scale need to be thoroughly studied under the background of global warming and glacier retreating.

Lacustrine environment responses to human activities in the past 300 years in Longgan Lake catchment, southeast China

The chronology of a gravity core sediment from Longgan Lake center was defined by 210Pb, combining with historic events recorded by document and sediment. The relationship between vegetation, soil erosion and lake nutrient state was discussed based on pollen, magnetic parameters, diatoms, phosphorus and pigments. The results show that the lake has undergone twice obvious transformations from oligotrophic to mesotrophic condition. Two eutrophications occurring at about 1768AD and the beginning of the 20th century respectively were related to external nutrient loading increase resulting from the enhanced human activities in the lake catchment. It is probable that strength of human actions in historic periods was influenced more or less by climatic changes. The lake eutrophication presented a more serious tendency because of the wide use of chemical fertilizer, reclamation of wetland and wetland vegetation destruction around the lake in the last 40 years.

Distribution of Macro-elements and Natural Radionuclides in the Bottom Sediments and Soils of the Catchment Areas of Small Lakes in the Baikal Region

The examination of macroelements and natural radionuclides in the bottom sediments of small lakes and soils in the catchment areas of the Baikal region allows for the study of the mechanism of inflow and the source of these materials.On the basis of the results of rentgenostructural analysis lake sediments are divided into four types:terrigenous,carbonate, terrigenous-carbonate and organogenic.Through the analysis of gamma-ray spectrometry and ato-

Salt lakes in China:Challenges for reconstructing ecological and climate variations

1 Introduction Studies on lakes have become an important concern for many scientists since it is well known that lakes can monitor detailed information about ecological,hydrological and sedimentary cycles which can be

Hydrological behaviour and water balance analysis for Xitiaoxi catchment of Taihu Basin

With the rapid social and economic development of the Taihu region, Taihu Lake now faces an increasingly severe eutrophication problem. Pollution from surrounding catchments contributes greatly to the eutrophication of water bodies in the region. Investigation of surface flow and associated mass transport for the Xitiaoxi catchment is of a significant degree of importance as the Xitiaoxi catchment is one of the major catchments within the Taihu region. A SWAT-based distributed hydrological model was established for the Xitiaoxi catchment. The model was calibrated and verified using hydrometeorological data from 1988 to 2001. The results indicate that the modeled daily and annual stream flow match the observed data both in the calibration period and the verification period, with a linear regression coefficient R2 and a coefficient e for modeled daily stream flow greater than 0.8 at Hengtangcun and Fanjiacun gauge stations. The results show that the runoff process in the Xitiaoxi catchment is affected both by rainfall and human activities （e.g., reservoirs and polder areas）. Moreover, the human activities weaken flood peaks more noticeably during rainstorms. The Water balance analysis reveals the percentages of precipitation made up by surface flow, evapotranspiration, groundwater recharge＇ and the change of soil storage, all of which are considered useful to the further understanding of the hydrological processes in the Xitiaoxi catchment. This study provides a good base for further studies in mass transport modeling and comparison of modeling results from similar hydrological models.

Zavkhan River and Its Catchment Area Delineation Using Satellite Image

The purpose of this research is to define initial parameters of Khyargas Lake-Zavkhan River and its catchment area using satellite images. The study has been done by two datasets: 1) Shuttle Radar Topography Mission (SRTM) at a horizontal spatial resolution of 90 meters, 2) The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) at a horizontal spatial resolution of 30 meters, using two different models of ArcHydro and Integrated Land and Water Information System (ILWIS) softwares. Main methods of models, that were used in this research are the Deterministic-8, the steepest slope, the spread, the seek computations and the trace analysis. Moreover, input data of the modeling are digital elevation model (DEM) and lake position, outlet location of the river. DEM based ArcHydro model was run on the both datasets, and ILWIS model was run on SRTM data. Several intermediate results were produced while the models run, and initial parameters of the Zavkhan River, its catchment area have been defined at the end of the model. Moreover, final results of the models were compared with each other and with the result of previous research, and with the reality. The result of this study can be used in baseline and advanced research on the catchment area. Besides of that, the result can define a spatial boundary of study on Zavkhan River and its catchment area. Moreover, it would have support for decision-making on ground and surface water resource, distribution and management. Further research, which will cover the entire territory of Mongolia, has to be done using same methodology. The 332nd decision on “River catchment areas of Mongolia” of the Minister of Nature, Environment and Tourism in 2009 has to renew, if a result of that study would be accepted from vocational organization and experts.

巢湖流域水生态系统状况变化研究

基于已开展的巢湖流域水域生物资源调查,综合2013、2023年水质、浮游植物、着生藻类、底栖动物和大型水生植物等资料,分析巢湖水域生物环境状况变化。结果表明:经过10年治巢项目的实施,巢湖流域整体水质有了明显改善,以南淝河和十五里河的水质改善最为明显。浮游植物群落组成发生较大变化,蓝藻门密度比由33.33%降为2.76%,硅藻门、金藻门密度比由11.43%、0.83%分别上升为26.62%、1.76%。底栖动物多样性呈上升趋势,耐污类群密度呈下降趋势。着生硅藻多样性指数总体呈增长趋势,优势群类依然主要为双壳缝目、无壳缝目和单壳缝目,大型水生植物群落优势种组成变化相对较小。本研究可为山水工程生态修复效果科学评估和生态修复方案制定提供数据支撑。

巢湖流域不同空间尺度土地利用对河流水体碳氮磷及其化学计量特征的影响

为更好地理解土地利用对水质和化学计量比的影响,本研究采用相关分析和冗余分析,定量探讨了2022年巢湖流域丰水期和平水期多个尺度土地利用与河流水体中总氮(TN)、总磷(TP)、化学需氧量(COD)浓度及C、N、P元素摩尔比的关系。结果表明:巢湖流域河流水体中的主要污染物是TN,与巢湖及全球尺度地表水平均值相比,其氮磷比(N︰P)偏高。在大部分研究尺度,TN、TP与建设用地占比呈显著(P<0.05)或极显著(P<0.01)正相关,与耕地占比无显著相关性,表明建设用地是TN、TP的重要来源。在子流域尺度,N︰P与建设用地占比呈极显著正相关(P<0.01),与耕地占比呈极显著负相关(P<0.01),表明建设用地占比的提升会加剧氮磷不平衡,而耕地占比的提升会缓解这一现象。土地利用对所有指标变异的总解释率在子流域尺度最高,各研究尺度土地利用的总解释率在丰水期更高。本研究结果可为巢湖流域的水质管理和土地利用规划提供理论指导。

巢湖流域山水林田湖草空间协调性评估

空间协调性评价可为提高国土空间利用效率提供数据支撑。本研究通过筛选符合巢湖流域特征、涵盖山水林田湖草各要素的指标,构建综合评价指标体系,并采用熵值法确定指标权重,基于耦合协调度模型分析2016—2021年巢湖流域三类空间耦合协调的时空分异特征。结果表明:2016—2021年巢湖流域耦合协调度为0.35~0.38,流域内三类空间处于轻度失调状态,三类空间的评价指数总体呈现生态空间指数>农业空间指数>城镇空间指数的特征,生态空间指数在巢湖流域空间协调性评价中的贡献最大;巢湖流域的空间布局呈“总体均衡,局部失衡”的特征,其中,六安市的耦合协调度高于其他4个城市,合肥市的耦合协调度低于其他4个城市,建议合肥市在发展城镇经济的同时,坚持多措并举优化农业结构,继续加大生态环境保护力度。研究结果可为巢湖流域的协调发展提供参考。

巢湖流域生物多样性评估指标体系构建

生物多样性评价是生物多样性保护与管理的基础。本研究基于压力-状态-响应(PSR)模型框架,构建了14个流域尺度指标以及23个生态系统尺度指标的巢湖流域生物多样性评价指标体系。该指标体系可全面反映生物多样性状态、变化、威胁和决策等综合因素的影响,为评估巢湖流域等长江中下游地区山水林田湖草系统保护修复成效、优化生物多样性保护策略提供指导。评价结果显示:2022年巢湖流域水环境一级保护区内湖泊、湿地生态系统的生物多样性水平均处于较高级别,系统反映了近10年巢湖的综合治理成效。

基于GIS的巢湖流域碳储量及碳汇现状研究

陆地生态系统的碳储量及碳汇研究可为国家实行“双碳”战略提供数据支撑。本文运用InVEST模型与CASA模型分别对巢湖流域的碳储量及固碳速率进行定量研究。结果表明:2022年巢湖流域碳储存总量为3350万t,NPP均值为469 g/(m^(2)·a),NEP均值为348.595 g/(m^(2)·a)。巢湖流域西南区大别山山区碳储量较高,合肥市城区内碳储量较低,该分布规律与巢湖流域固碳速率空间分布大致相似,且秋季固碳速率高于其它3个季度。土地利用类型是影响巢湖流域碳汇能力的重要因素之一,林地是巢湖流域碳密度与碳汇最高的土地类型,退耕还林是增加区域碳汇的重要手段。

气候变化和人类活动对鄱阳湖流域径流变化的影响研究

20个世纪60年代以来,鄱阳湖流域径流呈现出增加趋势,特别是1990年代流域径流增加显著,与该时期多次出现洪水灾害事件密切相关.运用Mann-Kendall检验法对1961—2000年流域径流序列进行突变分析,结果显示1992年附近是流域径流突变发生的拐点.基于径流对降雨和潜在蒸散发的敏感关系,以1961—1991年为基准期,定量分析了1992—2000年流域气候变化和人类活动对天然径流的影响分量.结果表明:相对于1961—1991年,1992—2000年多年平均径流量增加211.7mm,其中气候变化引起的增量为282.2mm,人类活动引起径流减小70.6mm,分别占多年平均径流变化量的133%和-33%.不同子流域间,气候变化和人类活动对径流的影响分量相差较大.气候变化因子中,流域降水量的增加,特别是夏季暴雨频率的增加,是引起1990年代鄱阳湖流域径流显著增大的主要原因,其次是蒸发量的长期下降.人类活动对鄱阳湖流域径流起着减流的作用,主要是由于流域内工农业的快速发展,大量水利工程设施的存在提高了水资源的利用程度;另一方面,1990年代流域水土流失状况的有效缓解,有助于增加流域的贮水能力,减小径流.

滇池流域典型城郊村镇排放污水氮、磷特征分析

城乡结合部地带的生活、生产排放污水已成为流域水体污染的主要原因之一,准确掌握城郊村镇排放污水规律及氮磷特征是区域环境治理的基本条件。本文以主要入滇池河道——大清河下游张家庙汇水区为研究区域,研究分析了滇池流域典型城郊村镇排放污水规律及其氮磷特征。结果表明,排放污水中总氮(TN)、总磷(TP)的浓度分别达(136.85±12.64～178.85±22.55)mg·L-1和(12.05±0.74～17.07±3.05)mg·L-1,其中氮主要以颗粒态氮(PN)、氨氮(NH4+-N)和溶解有机氮(DON)为主;磷主要以溶解性正磷酸盐(PO43--P)、颗粒态磷(PP)为主。一天之中排放污水流量和污染物浓度高峰出现在上午、中午和夜晚,低谷出现在清晨和傍晚;一周内工作日与非工作日的变化差异不显著;同一月份之中只有溶解态氮(DN)、溶解态磷(DP)浓度各天之间差异显著;不同月份之间污水排放流量、TN、DN、DP浓度差异显著。排放污水流量和污染物浓度变化基本反映了滇池流域典型城郊村镇居民的生活方式及作息规律,为该类区域污水治理提供资料参考。

滇池不同流域类型降雨径流对河流氮磷入湖总量的影响

通过对滇池三种不同流域类型的雨季初始期三场降雨径流的汇水河道的入湖口水质和流量监测 ,重点分析了典型城市纳污河流、城乡结合型河道和农业重污染区河道的营养盐携带状况与特征。研究结果表明 :不同流域类型河流的氮磷营养盐入湖总量受降雨过程及特征、流域类型特征、降雨径流流量、径流水营养盐浓度综合控制。城乡结合型河道 (大清河 )有最高的TP、KN (凯氏N)、NH3 N、NO3 N和NO2 N入湖总量 ,三场降雨累积量分别为11374 3、 12 7971 7、 85 36 5 4、 92 3 4和 84 1 2kg ;城市纳污河流 (乌龙河 )有最高的单位面积入湖总量负荷 ,TP、KN、NH3 N和NO2 N分别为 5 35 7、 5 86 0 5、 382 1 9和 2 4 6kg/km2 。