Statistical Interpretation of the Impact of Forest Growth on Streamflow of the Sameura Basin, Japan

A forested mountainous basin, the Sameura basin, located in Shikoku Island of Japan, experienced increased forest growth in the period from 1953 to 1994, like which occurred across the country. The impact of the forest growth on streamflow of the basin was assessed using statistical trend analysis. Annual maximum daily flow, annual minimum 5-day flow, and annual total runoff decreased by 55.8, 75.8, and 39.6%, respectively, over the period. However, the annual maximum 6-day, annual minimum 41-day, and annual total precipitation, respectively associated with annual maximum daily flow, annual minimum 5-day streamflow, and annual total runoff did not decrease. Annual and monthly temperature, which evapotranspiration positively related to, did not increase except in January. This demonstrates that the forest growth is responsible for the decrease in all these three flow regimes. The increase in evapotranspiration due to the forest growth resulted in the decrease in both total runoff and low flow. Thus, it seems that forest can hardly function to both reduce flood peaks during flood periods and increase water supply during drought periods.     

Analysis of agricultural drought using vegetation temperature condition index (VTCI) from Terra/MODIS satellite data

The most commonly used normalized difference vegetation index (NDVI) from remote sensing often fall short in real-time drought monitoring due to a lagged vegetation response to drought. Therefore, research recently emphasized on the use of combination of surface temperature and NDVI which provides vegetation and moisture conditions simultaneously. Since drought stress effects on agriculture are closely linked to actual evapotranspiration, we used a vegetation temperature condition index (VTCI) which is more closely related to crop water status and holds a key place in real-time drought monitoring and assessment. In this study, NDVI and land surface temperature (T _s) from MODIS 8-day composite data during cloud-free period (September–October) were adopted to construct an NDVI–T _s space, from which the VTCI was computed. The crop moisture index (based on estimates of potential evapotranspiration and soil moisture depletion) was calculated to represent soil moisture stress on weekly basis for 20 weather monitoring stations. Correlation and regression analysis were attempted to relate VTCI with crop moisture status and crop performance. VTCI was found to accurately access the degree and spatial extent of drought stress in all years (2000, 2002, and 2004). The temporal variation of VTCI also provides drought pattern changes over space and time. Results showed significant and positive relations between CMI (crop moisture index) and VTCI observed particularly during prominent drought periods which proved VTCI as an ideal index to monitor terminal drought at regional scale. VTCI had significant positive relationship with yield but weakly related to crop anomalies. Duration of terminal drought stress derived from VTCI has a significant negative relationship with yields of major grain and oilseeds crops, particularly, groundnut.     

Quality of Shallow Groundwater and Drainage Water in Irrigated Agricultural Lands in A Mediterranean Coastal Region of Turkey

Spatial and seasonal differences in water quality of drainage water and unconfined shallow groundwater were related to irrigation in Samandağ, a Mediterranean coastal region. Eighteen wells, seven drainage points and Orontes River were monitored bimonthly for one year for analyses of electrical conductivity (EC), total dissolved solids (TDS), sodium adsorption ratio (SAR), cations (Na, K, Ca + Mg) and anions (CO₃, HCO₃, Cl and SO₄). Agricultural irrigation using saline groundwater decreased water quality of Orontes River during the irrigation season (May to September) more than during the non-irrigation season (October to April). Seasonal fluctuations in water quality of shallow groundwater were greater during the irrigation season than the non-irrigation season in the study area. Excessive use of groundwater resulted in a decline in the water table levels in the irrigation season. Water table level rose up to the soil surface in areas where there was a lack of drainage or poor drainage, due to the impact of precipitation in the winter. SAR and pH values of drainage water increased in the irrigation season, while the other properties of drainage water decreased. Irrigation water quality of Orontes River was classified as C₃S₁ in both seasons. Irrigation water quality of shallow groundwater and drainage water varied from C₂S₁ to C₄S₂ in one year. Drainage and well waters were found to be different on yearly basis in terms of Na, SAR (p<0.01) and Ca + Mg concentrations (p<0.001). Ca + Mg concentrations for both sources were different for all sampling dates (p<0.001).     

Analysis of Historical Salinity and Boron Surface Water Monitoring Data from the San Joaquin River Watershed: 1985–2002

The objectives of this study were to use both parametric and probabilistic approaches to analyze water column concentrations of both salinity (24,845 measurements) and boron (13,028 measurements) from numerous investigations conducted in the San Joaquin River watershed from 1985 to 2002 to assess spatial and temporal trends and determine the probability of exceeding regulatory targets during both the irrigation and non-irrigation season. Salinity and boron concentrations from 26 mainstem and tributary sites were highly correlated based on this 17 yr data set. Generally, salinity and boron concentrations were higher in winter/spring and lower in summer/fall; higher concentrations of both constituents were reported in tributary sites when compared with the mainstem San Joaquin River. Approximately half the sites showed showed a negative correlation between flow and both constituents. Concentrations of both salinity and boron were somewhat variable with flow conditions for the other sites. Both linear and curvilinear trends were inconsistent over time. The salinity 90th centiles for the 26 sites ranged from 143 to 7,559 micros cm(-1) with the highest 90th centiles in tributary sites. Probabilistic analysis of salinity 90th centiles by year for five sites with extensive data showed a significant decrease over time at two sites and no significant trend for the other three sites. The probability of exceeding the salinity targets during either the irrigation (700 microm cm(-1)) or non-irrigation (1,000 micros cm(-1)) season was greater than 19% for all but three sites. The boron 90th centiles for the 26 sites ranged from 0.41 to 13.6 mg L(-1) with the highest 90th centiles from tributary sites. Probabilistic analysis of the boron 90th centile values by year for the five sites with the most extensive data showed a significant decrease over time at two sites and no significant trend for the other three sites. The probability of exceeding the boron target during the irrigation season (0.80 mg L(-1)) and non-irrigation (1.0 mg L(-1)) season was greater that 18% for all but three sites. Results from this analysis have important regulatory implications as targets for both salinity and boron are frequently exceeded at various sites in the San Joaquin River watershed.     

Drought impact assessment from monitoring the seasonality of vegetation condition using long-term time-series satellite images: a case study of Mt. Kenya region

Drought-induced anomalies in vegetation condition over wide areas can be observed by using time-series satellite remote sensing data. Previous methods to assess the anomalies may include limitations in considering (1) the seasonality in terms of each vegetation-cover type, (2) cumulative damage during the drought event, and (3) the application to various types of land cover. This study proposed an improved methodology to assess drought impact from the annual vegetation responses, and discussed the result in terms of diverse landscape mosaics in the Mt. Kenya region (0.4° N 35.8° E?~?1.6° S 38.4° E). From the 30-year annual rainfall records at the six meteorological stations in the study area, we identified 2000 as the drought year and 2001, 2004, and 2007 as the normal precipitation years. The time-series profiles of vegetation condition in the drought and normal precipitation years were obtained from the values of Enhanced Vegetation Index (EVI; Huete et al. 2002), which were acquired from Terra MODIS remote sensing dataset (MOD13Q1) taken every 16 days at the scale of 250-m spatial resolution. The drought impact was determined by integrating the annual differences in EVI profiles between drought and normal conditions, per pixel based on nearly same day of year. As a result, we successfully described the distribution of landscape vulnerability to drought, considering the seasonality of each vegetation-cover type at every MODIS pixel. This result will contribute to the large-scale landscape management of Mt. Kenya region. Future study should improve this method by considering land-use change occurred during the long-term monitoring period.     

Assessing Multi-site Drought Connections in Iran Using Empirical Copula

Drought is a multi-dimensional natural hazard with stochastic characteristics usually related to each other. Separate univariate statistical models cannot capture the important relationships among drought characteristics, that is, severity and duration. In this study, an empirical copula is employed to construct a bivariate model of droughts, where droughts are defined as continuously negative standardized precipitation index (SPI) periods with one SPI value reaching ?1 or less. Bivariate frequency analyses in terms of recurrence intervals are performed using the established empirical copula-based bivariate drought model. The inter-connection among different regions of droughts is explored by a lower tail dependence coefficient. A nonparametric estimation based on an empirical copula is employed pairwisely to calculate the lower tail dependence coefficient among stations. The proposed method is applied to six rainfall gauge stations in Iran to explore drought properties of single sites as well as the inter-connection among multi-sites. The results show that greater mean drought severity and duration are associated with the least arrival rate of drought events, which occurs at the Ahwaz station. The tail dependence analysis reveals that distance between stations is not a key parameter. Generally, the Ahwaz and Isfahan stations have the highest probability of simultaneous droughts among the six stations.     

IWQ Index: A GIS-Integrated Technique to Assess Irrigation Water Quality

The irrigation water quality and the associated hazards to soil characteristics and crop yield is often a complex phenomenon that involves the combined effect of many parameters. From a management point of view, it is sometimes necessary to analyze all related parameters as a combination rather than focusing on a single isolated parameter. With this objective in mind, a new GIS-integrated tool is proposed in this study to evaluate the quality of irrigation waters with regards to potential soil and crop problems. The proposed procedure is mainly an index method that utilizes five hazard groups: (a) salinity hazard, (b) infiltration and permeability hazard, (c) specific ion toxicity, (d) trace element toxicity; and, (e) miscellaneous impacts on sensitive crops. A linear combination of these groups is formulated to form the so-called IWQ index, which is a technique that could be used to classify irrigation waters with respect to three suitability classes. The proposed technique is applied to assess the irrigation water quality of the Simav Plain located in western Anatolia, Turkey. The Simav application is implemented by using a GIS database developed for the plain. Based on the results of this application, the general groundwater quality in the surfacial aquifer is found to be fairly good and the aquifer waters are mostly suitable for irrigation purposes.     

指标动态权重对湖泊水生态系统健康评价影响研究

利用2014年和2018年鄱阳湖丰〖CD*2〗涨〖CD*2〗枯〖CD*2〗退4个水文时期的监测数据,引入可拓评价法对鄱阳湖水生态系统健康进行评价并探讨指标动态权重的影响。结果表明：鄱阳湖水生态系统健康状态不同水文时期差异显著,退水期最优,枯水期最差,涨水期稍优于丰水期。鄱阳湖水生态系统健康评价指标权重具有动态变化特征,指标权重值会随着指标具体取值的不同而发生变化,即便指标值相同,各指标间关系不同,指标权重也不同,从而影响鄱阳湖水生态系统健康的评价结果。鄱阳湖不同时期生态系统功能和结构差异较大,采用动态的权重对其水生态系统健康评价相对更加合理。     

生物监测在航道疏浚工程环境影响评价中的应用

通过生物监测手段对长江口宝山北水道航道疏浚工程进行了生态环境影响跟踪监测和评价.结果发现,工程结束后生物优势种和多样性指数与环评同期相比基本稳定,施工期间生态指标密度和生物量有所波动.监测评价结果反映了疏浚工程的施工对长江口的生态环境影响有限,并随着工程结束周边水域环境正日益恢复.     

生态修复后某矿区下游农田土壤金属污染特征与风险评价

为研究广东省某矿区开展生态修复多年后下游农田土壤的金属污染状况,选取该矿区下游某村周边农田土壤及灌溉水渠作为研究对象,对该区域采集了40个土壤表层样本和8个水体样本,利用Arcgis软件对农田土壤样品中As、Cu、Cd、Pb、Zn、Mn和Fe₂O₃的质量分数进行克里金空间插值,解析该区域农田土壤金属的空间分布特征;采用综合污染指数法和潜在生态风险指数法对该区域耕作层土壤中As、Cu、Cd、Pb、Zn和Mn进行风险评价。结果表明,40个土壤样品中As、Cd、Cu、Zn和Pb的超标率分别为77.5%、70%、87.5%、27.5%和67.5%,说明调查区域农田土壤污染属于多金属复合污染,且对农作物的生产和安全产生巨大的威胁。部分土壤样品中As、Pb和Cd含量超过了中国农用地土壤污染风险管制值,需采取严格管控措施。通过分析土壤金属的空间分布,发现土壤金属含量超标点位主要位于灌溉口与受污染河流周边,且含量与离灌溉口距离成反比。结合目前灌溉水样中的金属均未超标的情况,得出该区域农田土壤污染是由该矿区生态环境修复前所产生的含金属灌溉水导致土壤中金属的积累...     

Early-season agricultural drought: detection, assessment and monitoring using Shortwave Angle and Slope Index (SASI) data

Early season or crop-planting-period (ES/CPP) drought conditions have become a recurrent phenomenon in tropical countries like India, due to fluctuations in the time of onset and progression of monsoon rains. ES/CPP agricultural drought assessment is a major challenge because of the difficulties in the generation of operational products on soil moisture at larger scales. The present study analyzed the Shortwave Angle Slope Index (SASI) derived from Near Infrared and Shortwave Infrared data of Moderate Resolution Imaging Spectroradiometer, for tracking surface moisture changes and assessing the agricultural drought conditions during ES/CPP, over Andhra Pradesh state, India. It was found that in-season progression of SASI was well correlated with rainfall and crop planting patterns in different districts of the study area state in both drought and normal years. Rainfall occurrence, increase in crop planted area, and decrease in SASI were in chronological synchronization in the season. Change in SASI from positive to negative values is a unique indication of dryness to wetness shift in the season. Duration of positive SASI values indicated the persistence of agricultural drought in the crop planting period. Mean SASI values were able to discriminate an area which was planted in normal year and unplanted in drought year. SASI thresholds provide an approximate and rapid estimate of the crop planting favorable area in a region which is useful to assess the impact of drought. Thus, SASI is a potential index to strengthen the existing operational drought monitoring systems. Further work needs to be on the integration of multiple parameters—SASI, soil texture, soil depth, rainfall and cropping pattern, to evolve a geospatial product on crop planting favorable areas. Such products pave the way for quantification of drought impact on agriculture in the early part of the season, which is a major inadequacy in the current drought monitoring system.     

Integral assessment of climate impact on the transboundary Mesta River flow formation in Bulgaria

The present work considers the section of the Mesta River on Bulgarian territory using the integral method for evaluation of climate and anthropogenic impact on the river flow. The level of this impact is determined by the index K _i (flow module), the coefficient C _i for the deviation of the average annual water volume Q _i from the flow norm Q _o and the index h _i for the deviation of the average annual rainfall volume H _i from the average multi-annual rainfall volume H _o . The dynamics of the average annual flow Q _i at two typical hydrometric stations – Yakoruda and Khadzhidimovo, as well as the dynamics of the average annual rainfall for the Yakoruda station was examined for the period 1955–2003. The data for the considered period 1955–2003 exhibit a decreasing trend of the average annual water volumes dynamics for both stations due to the impact of climate changes in the Mesta River catchment.     

Agro-economic evaluation of water resource project--a modeling approach

Feasibility of an irrigation project is evaluated by two criteria viz., reservoir capacity to irrigate its command area and economic returns by incremental crop production versus capital investment for dam construction. The annual water requirement of different crops in the command area is estimated and compared with the availability of water from the dam for irrigation purpose. The annual crop water requirement is estimated as the sum of evapotranspiration for crops and transmission and other losses. Evapotranspiration is estimated by modified Penman formula. Economics of crop production is analyzed by first estimating the monetary value of existing crop production under current rain fed conditions and then estimating the incremental production of irrigated command area for the proposed crop pattern. The proposed cropping pattern is prepared so as to maximize the benefit of crop production and fodder requirement while maintaining a better crop rotation to improve and maintain physical, chemical, and biological conditions of the soil. The dam is to be used for irrigation and water supply only. Command area served by this reservoir will be 76,500 ha. The existing annual agricultural return is Rs. 2995.56 lakhs and with the proposed irrigation scheme, it is estimated as Rs. 1,77,91.90 lakhs. The incremental annual return would be Rs. 1,47,96.35 lakhs i.e., 642.68% increase in annual return.     

利用植被供水指数法监测干旱的研究

利用FY-1D/AVHRR数据通道1、2的反射率计算植被指数和通道4、5的亮温计算作物冠层温度,进而求出植被供水指数可监测干旱状况.本文简单介绍了利用FY-1D/AVHRR数据植被供水指数法监测生长季的干旱状况.研究表明,该方法所得结果从总体趋势看,与实际情况基本吻合.因此,植被供水指数法适用于生长季大范围的干旱监测.     

黑龙江省“十三五”时期生态环境质量变化及趋势预测

以黑龙江省生态环境监测网监测结果为基础,总结归纳了"十三五"期间黑龙江省生态环境质量变化特征,并采用随机森林和GM(1,1)预测模型对"十四五"期间黑龙江省生态环境质量状况进行了预测。结果表明:"十三五"期间,黑龙江省环境空气、水环境和声环境质量全面好转。其中,环境空气主要污染物PM_2.5、PM₁₀、SO₂、NO₂和CO的年均质量浓度均呈现出明显下降的趋势,"哈大绥"重点区域PM₁₀、SO₂、NO₂和CO年均质量浓度呈现下降趋势。地表水水质总体呈波动变化趋势,水质状况均为轻度污染。"十四五"期间,黑龙江省生态环境质量将处于稳中向好的趋势。环境空气主要污染物及地表水主要污染指标年均质量浓度均呈现明显的下降趋势,道路交通声环境质量也将得到进一步改善。     

Tree-ring analysis for the assessment of anthropogenic changes and trends

Investigation of Pine (Pinus sylvestris L.)annual radial increment (width of annual tree rings) was carriedout in the surroundings of one of the largest pollution sources inLithuania – Jonava Nitrogen Fertilizers Plant. The main objectiveof investigation was to analyse different sides of anthropogenictransformations of tree-ring series in the polluted environment:changes in tree growth intensity; variance changes in tree-ringseries; changes in the relations with natural external factors.Three different periods of tree reaction to the environmentalpollution were singled out – fertilization period, depressionperiod and recovery period since annual emissions were essentiallyreduced. The variance of tree-ring series has increased severaltimes in the polluted environment. Reaction of trees to the impactof climatic factors (temperature, precipitation) has changedsignificantly in the polluted environment and their sensitivity hasalso increased.     

Comparison of mass concentrations of SO2 determined in air by two different methods

Mass concentrations of sulphur dioxide were determined in parallel 24-hour samples of ambient air at a measuring site in Zagreb during a period of eight years. The methods used were the West-Gaeke's tetrachloromercurate-pararosaniline method (TCM) and the Standard British Method (SBM). Total results for the annual intervals of measuring were analyzed statistically and also discussed separately for winter and summer periods, in order to see whether they are influenced by seasonal rhythm.     

Response of non-point source pollutant loads to climate change in the Shitoukoumen reservoir catchment

The impacts of climate change on streamflow and non-point source pollutant loads in the Shitoukoumen reservoir catchment are predicted by combining a general circulation model (HadCM3) with the Soil and Water Assessment Tool (SWAT) hydrological model. A statistical downscaling model was used to generate future local scenarios of meteorological variables such as temperature and precipitation. Then, the downscaled meteorological variables were used as input to the SWAT hydrological model calibrated and validated with observations, and the corresponding changes of future streamflow and non-point source pollutant loads in Shitoukoumen reservoir catchment were simulated and analyzed. Results show that daily temperature increases in three future periods (2010–2039, 2040–2069, and 2070–2099) relative to a baseline of 1961–1990, and the rate of increase is 0.63°C per decade. Annual precipitation also shows an apparent increase of 11 mm per decade. The calibration and validation results showed that the SWAT model was able to simulate well the streamflow and non-point source pollutant loads, with a coefficient of determination of 0.7 and a Nash–Sutcliffe efficiency of about 0.7 for both the calibration and validation periods. The future climate change has a significant impact on streamflow and non-point source pollutant loads. The annual streamflow shows a fluctuating upward trend from 2010 to 2099, with an increase rate of 1.1 m³ s⁻¹ per decade, and a significant upward trend in summer, with an increase rate of 1.32 m³ s⁻¹ per decade. The increase in summer contributes the most to the increase of annual load compared with other seasons. The annual NH₄⁺-N load into Shitoukoumen reservoir shows a significant downward trend with a decrease rate of 40.6 t per decade. The annual TP load shows an insignificant increasing trend, and its change rate is 3.77 t per decade. The results of this analysis provide a scientific basis for effective support of decision makers and strategies of adaptation to climate change.     

Comparison of spatial interpolation methods for soil moisture and its application for monitoring drought

Soil moisture data can reflect valuable information on soil properties, terrain features, and drought condition. The current study compared and assessed the performance of different interpolation methods for estimating soil moisture in an area with complex topography in southwest China. The approaches were inverse distance weighting, multifarious forms of kriging, regularized spline with tension, and thin plate spline. The 5-day soil moisture observed at 167 stations and daily temperature recorded at 33 stations during the period of 2010–2014 were used in the current work. Model performance was tested with accuracy indicators of determination coefficient (R ²), mean absolute percentage error (MAPE), root mean square error (RMSE), relative root mean square error (RRMSE), and modeling efficiency (ME). The results indicated that inverse distance weighting had the best performance with R ², MAPE, RMSE, RRMSE, and ME of 0.32, 14.37, 13.02%, 0.16, and 0.30, respectively. Based on the best method, a spatial database of soil moisture was developed and used to investigate drought condition over the study area. The results showed that the distribution of drought was characterized by evidently regional difference. Besides, drought mainly occurred in August and September in the 5 years and was prone to happening in the western and central parts rather than in the northeastern and southeastern areas.     

Evaluation of stream chemistry trends in US Geological Survey reference watersheds, 1970–2010

The Hydrologic Benchmark Network (HBN) is a long-term monitoring program established by the US Geological Survey in the 1960s to track changes in the streamflow and stream chemistry in undeveloped watersheds across the USA. Trends in stream chemistry were tested at 15 HBN stations over two periods (1970–2010 and 1990–2010) using the parametric Load Estimator (LOADEST) model and the nonparametric seasonal Kendall test. Trends in annual streamflow and precipitation chemistry also were tested to help identify likely drivers of changes in stream chemistry. At stations in the northeastern USA, there were significant declines in stream sulfate, which were consistent with declines in sulfate deposition resulting from the reductions in SO₂ emissions mandated under the Clean Air Act Amendments. Sulfate declines in stream water were smaller than declines in deposition suggesting sulfate may be accumulating in watershed soils and thereby delaying the stream response to improvements in deposition. Trends in stream chemistry at stations in other part of the country generally were attributed to climate variability or land disturbance. Despite declines in sulfate deposition, increasing stream sulfate was observed at several stations and appeared to be linked to periods of drought or declining streamflow. Falling water tables might have enhanced oxidation of organic matter in wetlands or pyrite in mineralized bedrock thereby increasing sulfate export in surface water. Increasing sulfate and nitrate at a station in the western USA were attributed to release of soluble salts and nutrients from soils following a large wildfire in the watershed.