Assessment of land use land cover change impact on hydrological regime of a basin

The sustainability of water resources mainly depends on planning and management of land use; a small change in it may affect water yield largely, as both are linked through relevant hydrological processes, explicitly. However, human activities, especially a significant increase in population, in-migration and accelerated socio-economic activities, are constantly modifying the land use and land cover (LULC) pattern. The impact of such changes in LULC on the hydrological regime of a basin is of widespread concern and a great challenge to the water resource engineers. While studying these impacts, the issue that prevails is the selection of a hydrological model that may be able to accommodate spatial and temporal dynamics of the basin with higher accuracy. Therefore, in the present study, the capabilities of variable infiltration capacity hydrological model to hydrologically simulate the basin under varying LULC scenarios have been investigated. For the present analysis, the Pennar River Basin, Andhra Pradesh, which falls under a water scarce region in India, has been chosen. The water balance components such as runoff potential, evapotranspiration (ET) and baseflow of Pennar Basin have been simulated under different LULC scenarios to study the impact of change on hydrological regime of a basin. Majorly, increase in built-up (13.94% approx.) and decrease in deciduous forest cover (2.44%) are the significant changes observed in the basin during the last three decades. It was found that the impact of LULC change on hydrology is balancing out at basin scale (considering the entire basin, while routing the runoff at the basin outlet). Therefore, an analysis on spatial variation in each of the water balance components considered in the study was done at grid scale. It was observed that the impact of LULC is considerable spatially at grid level, and the maximum increase of 265 mm (1985–2005) and the decrease of 48 mm (1985–1995) in runoff generation at grid were estimated. On the contrary, ET component showed the maximum increase of 400 and decrease of 570 mm under different LULC change scenario. Similarly, in the base flow parameter, an increase of 70 mm and the decrease of 100 mm were observed. It was noticed that the upper basin is showing an increasing trend in almost all hydrological components as compared to the lower basin. Based on this basin scale study, it was concluded that change in the land cover alters the hydrology; however, it needs to be studied at finer spatial scale rather than the entire basin as a whole. The information like the spatial variation in hydrological components may be very useful for local authority and decision-makers to plan mitigation strategies accordingly.     

Climate and hydrological models to assess the impact of climate change on hydrological regime: a review

Quantitative knowledge about the impacts of climate change on the hydrological regime is essential in order to achieve meaningful insights to address various adverse consequences related to water such as water scarcity, flooding, drought, etc. General circulation models (GCMs) have been developed to simulate the present climate and to predict future climatic change. But, the coarse resolution of their outputs is inefficient to resolve significant regional scale features for assessing the effects of climate change on the hydrological regimes, thus restricting their direct implementation in hydrological models. This article reviews hierarchy and development of climate models from the early times, importance and inter-comparison of downscaling techniques and development of hydrological models. Also recent research developments regarding the evaluation of climate change impact on the hydrological regime have been discussed. The article also provides some suggestions to improve the effectiveness of modelling approaches involved in the assessment of climate change impact on hydrological regime.     

Water system characteristics of Karst river basins in South China and their driving mechanisms of hydrological drought

Natural Hazards - It is common knowledge that drought is considered one of the most damaging natural disasters in terms of economic costs, societal problems, and ecological impacts. In this study,...     

水文双变量重现期分析及在干旱中应用

单变量水文统计中一些广为接受的概念在多变量环境下尚缺乏深入分析,也易被误解,如N年内重现期大于等于T的多变量事件发生的次数与N/T的关系。实践中,多变量联合重现期与其边缘分布变量重现期的一些经验关系被发现并通过了案例验证分析,但缺乏解释和推导。基于GH Copula推导了双变量联合重现期与边缘分布变量重现期的关系以及双变量事件发生次数与其重现期、变量相关程度间的定量关系。以昆明56年的逐月SPI(Standardized Precipitation Index)和SRI(Standardized Runoff Index)识别了干旱事件,采用GH Copula构建了干旱历时和烈度的联合分布函数,验证了双变量联合重现期与边缘分布变量重现期的关系以及多变量事件发生次数与其重现期的定量关系。表明不宜以“and”第1重现期是否接近于比该干旱事件的旱情更重的干旱发生的平均时间间隔来说明干旱特征值重现期分析的合理性。变量的相关性不强时,需谨慎采用边缘分布变量重现期的较大值近似代替“and”事件的第1重现期。     

Use of hydrological methods for assessment of environmental flow in a river reach

Environmental flow assessment and maintenance are relatively new practices, especially in developing countries. This paper describes the desktop assessment of environmental flows in a river with insufficient data on ecological features and values. In this study, the potential environmental flows in a typical river reach of the Shahr Chai River in Iran were investigated using a newly developed hydrological method (flow duration curve (FDC) shifting) and Global Environmental Flow Calculator software. This approach uses monthly flow data to develop an environmental FDC and to generate flow requirements corresponding to different features of the river ecosystem. Results were compared with those from four alternative hydrological methods: the desktop reserve model (DRM), Tennant, low-flow index, and flow duration curve analysis (FDCA). Comparisons of these methods indicated that to maintain the basic function of the river ecosystem, the river flows should be managed within an acceptable environmental level. The predictions from the Tennant method and the low-flow index (7-day low flow with a 10-year return period), and from the FDCA (for flows exceeding 90?% of occurrence) are not as reliable as those from the FDC shifting technique and DRM. Comparative results indicate that a minimum flow rate of 1.2?m³/s (equivalent to 23?% of the natural mean annual runoff, or flow with 80?% occurrence depicted from the FDC) is required for the Shahr Chai River to run toward the internationally recognized Urmia Lake in Iran.     

Impact of water demand on hydrological regime under climate and LULC change scenarios

The present study focuses on an assessment of the impact of future water demand on the hydrological regime under land use/land cover (LULC) and climate change scenarios. The impact has been quantified in terms of streamflow and groundwater recharge in the Gandherswari River basin, West Bengal, India. dynamic conversion of land use and its effects (Dyna-CLUE) and statistical downscaling model (SDSM) are used for quantifying the future LULC and climate change scenarios, respectively. Physical-based semi-distributed model Soil and Water Assessment Tool (SWAT) is used for estimating future streamflow and spatiotemporally distributed groundwater recharge. Model calibration and validation have been performed using discharge data (1990–2016). The impacts of LULC and climate change on hydrological variables are evaluated with three scenarios (for the years 2030, 2050 and 2080). Temperature Vegetation Dyrness Index (TVDI) and evapotranspiration (ET) are considered for estimation of water-deficit conditions in the river basin. Exceedance probability and recurrence interval representation are considered for uncertainty analysis. The results show increased discharge in case of monsoon season and decreased discharge in case of the non-monsoon season for the years 2030 and 2050. However, a reverse trend is obtained for the year 2080. The overall increase in groundwater recharge is visible for all the years. This analysis provides valuable information for the irrigation water management framework.     

喜马拉雅山北坡典型冰川流域水文过程比较研究北大核心CSCD

2005年为喜马拉雅山中段的暖干年,夏季气温为历年最高。本文利用2005年珠穆朗玛峰绒布冰川下游水文观测资料及附近定日气象站资料、羊卓雍湖卡鲁雄曲冰川流域水文资料及附近浪卡子站气象资料,分析了两个流域的融水过程,建立冰雪消融数值模型,并进行了对比研究。结果表明:统计相关得到两流域气温和降水高度相关性(r>0.8),说明在区域尺度上两个地区的气候过程相似。绒布冰川消融强度比卡鲁雄曲冰川约大2倍,冰川退缩速率二者也差2.5倍,说明用冰川消融气温估计的水量损失基本反映两地冰川变化的事实。本文提出的冰雪融水模型,可以用于两个冰川区之间广大无资料冰川流域融水及冰川变化的估计,以及恢复珠穆朗玛和喜马拉雅山脉其他地区的长期水文过程及水资源变化的计算。     

Assessment of a conceptual hydrological model and artificial neural networks for daily outflows forecasting

Artificial neural networks (ANNs) are used by hydrologists and engineers to forecast flows at the outlet of a watershed. They are employed in particular where hydrological data are limited. Despite these developments, practitioners still prefer conventional hydrological models. This study applied the standard conceptual HEC-HMS’s soil moisture accounting (SMA) algorithm and the multi layer perceptron (MLP) for forecasting daily outflows at the outlet of Khosrow Shirin watershed in Iran. The MLP [optimized with the scaled conjugate gradient] used the logistic and tangent sigmoid activation functions resulting into 12 ANNs. The R ² and RMSE values for the best trained MPLs using the tangent and logistic sigmoid transfer function were 0.87, 1.875 m³ s^?1 and 0.81, 2.297 m³ s^?1, respectively. The results showed that MLPs optimized with the tangent sigmoid predicted peak flows and annual flood volumes more accurately than the HEC-HMS model with the SMA algorithm, with R ² and RMSE values equal to 0.87, 0.84 and 1.875 and 2.1 m³ s^?1, respectively. Also, an MLP is easier to develop due to using a simple trial and error procedure. Practitioners of hydrologic modeling and flood flow forecasting may consider this study as an example of the capability of the ANN for real world flow forecasting.     

分布式水文模型中河流水深及其与地下水相互作用的耦合模拟

大尺度流域水文模型一般只模拟河道径流,对河流水深和流速并不关注。在进行河流-地下水相互作用模拟时,河流水深（水位）是一个重要因素,其时空变化及其对河流-地下水水量交换的影响应加以考虑。本文就流域分布式水文模型中河流水深的时空变化计算及其与地下水的实时耦合模拟进行了研究,提出了相应的计算方法,改进了大尺度水文模型WATLAC,并通过V-型流域考题进行了检验。模拟结果显示,模型有效地模拟了V-型流域的河流水深、地下水水位沿河道的时空变化以及河流与地下水的水交换量,揭示了河流-地下水相互作用关系在降雨过程中的变化规律及主控因子。此外就河床糙率对河流水深及河流与地下水间水交换量的影响做了模拟分析,发现河床糙率的改变将影响河流水深,从而进一步影响河流与地下水的水交换量。本文提出的算法较为真实地模拟了河流洪水演进过程及其对河流-地下水相互作用的影响,模型适用于河流-地下水相互作用明显的区域,可作为评估地表-地下水相互影响的有效计算工具。     

水沙变异条件下的河流系统调整及其研究进展

保持河流各方面整体协调是流域开发研究的重点和必然趋势,研究水沙变异条件下河流系统的调整机理,对于河流健康的保障具有重要意义.总结分析了水沙变异与河流系统的作用特性,明确了河流系统中水文、水力、地貌、生态等方面的各种调整实际上是与系统输入特性的特定变化相联系的;回顾了对河流系统及其功能的认识过程与研究现状,展望了将来的研究趋势.     

Impact of city expansion on hydrological regime of Rispana Watershed,Dehradun, India

Rispana River flows through the heart of Dehradun, the capital city of Uttarakhand State, India. Uttarakhand had separated from Uttar Pradesh State in the year 2000; since then, Dehradun City has witnessed numerous changes. Both urban sprawl and densification were noticed, with around a 32% increase in population. The city had faced recurrent high runoff and urban flood situations in these last 2 decades. Therefore, the study was conducted to detect the change in land use/land cover (LULC), especially urbanization, through remote sensing data; and later to determine the impacts of such changes on the Rispana watershed hydrology. The LULC maps for the year 2003 and the 2017 were generated through supervised classification technique using the Landsat Series satellite datasets. The LULC change analysis depicted that mainly the urban settlement class increased with significant area among other classes from the year 2003–2017. It was noticed that majorly agriculture and fallow land (8.18 km², which is 13.52% of total watershed area) converted to urban, increasing the impervious area. Almost all the municipal wards, falling in the Rispana watershed, showed urbanization during the said period, with an increase of as high as 71%. The change in LULC or effect of urbanization on the hydrological response of the watershed was assessed using the most widely used Natural Resources Conservation Services Curve Number method. It was noticed that the area under moderated runoff potential (approx. 10.23 km²) steeply increased during the lean season, whereas, high runoff potential zones (5 km²) increased significantly under wet season. Therefore, it was concluded that an increase in impervious surface resulted in high runoff generation. Further, such LULC change along with climate might lead to high runoff within the watershed, which the present storm drainage network could not withstand. The situation generally led to urban floods and affected urban dwellers regularly. Therefore, it is critical to assess the hydrological impacts of LULC change for land use planning and water resource management. Furthermore, under the smart city project, the local government has various plans to improve present infrastructure; therefore, it becomes necessary to incorporate such observations in the policies.

     

贵州深切峡谷区典型岩溶地下河水文水化学特征

黔中水利枢纽水源工程——平寨水库位于贵州高原三岔河深切峡谷型岩溶区,是保障黔中地区水资源安全的重要水利基础设施。文章采用水文水化学自动监测技术,对前期水文地质基础研究较为薄弱的平寨水库区间流域内的重要支流——三塘地下河系统的水文水化学变化规律进行了研究,在此基础上探讨了深切峡谷型岩溶地下河系统的岩溶发育规律及管道模式。研究结果表明,该地下河系统水化学动态主要受覆被CO₂效应、有效降雨稀释效应和径流-排泄通道开放效应三者的控制。在不同时间尺度和大气降水条件下,水化学动态的总体变化特征不同,起主导作用的效应也有所不同。水温在年尺度上呈夏季高冬季低的变化规律,日尺度上呈昼高夜低的变化规律。电导率和水中CO₂分压的动态变化,年尺度下,在覆被CO₂效应与稀释效应的共同作用下总体呈现平水期较高丰水期较低;月尺度下,降雨初期可见明显的覆被CO₂效应,降雨后则为有效降雨的稀释效应主控;在旱季无雨条件下的日尺度上,可见由径流-排泄通道的开放效应造成的水化学日动态。径流-排泄通道开放效应的识别,可为今后在岩溶水系统模型化研究中判断岩溶管道的承压状态提供水化学方面的依据。本研究对今后该区开展地表与地下水库联合调度、水资源合理利用研究提供了一定的水文地质基础。     

敦化市区地下水动态特征

本文按不同地下水类型,从地下水的水位、水温、水质三个方面论述了敦化市规划区地下水的动态特征。     

Assessing the effects of climate change on the hydrological regime of the Limay River basin

The electricity generation capacity in the Limay River basin is approximately 26% of the total electrical power generation in Argentina. Assessing the potential effects of climate change on the hydrological regime of this basin is an important issue for water resources management. This study explores the presence of trends in streamflow series, evaluates climate sensitivity and studies the effects on the flow regime of predicted changes in precipitation in the basin. In order to identify and quantify changes in observed streamflow series, the Mann–Kendall test, with a modification for autocorrelated data, and an estimator of the magnitude of the trend are applied. In order to evaluate the sensitivity of streamflow to changes in climate, the concept of elasticity is used. Precipitation elasticity of streamflow is used to quantify the sensitivity of streamflow to changes in precipitation and is estimated using a power law model and a linear statistical model in two sub-basins, Aluminé and Nahuel Huapi. The effects on flow regime of the predicted changes in precipitation under different scenarios are studied. Climatic results for different scenarios of growth in greenhouse gases from some General Circulation Models are used as inputs into the proposed models. The analysis identifies decreasing trends in mean and minimum annual flows and in the low flow season. The estimates of the precipitation elasticity imply that changes in precipitation produce similar changes in streamflow and the climatic results for different scenarios show that the variations are moderate.     

短期水文气象资料估算哈尔滨至同江冰厚度

为估算松花江干流哈尔滨至同江段相距660 km的河冰厚度分布,用松花江干流短期实测水文和气象资料,在静态水域斯蒂芬冰厚计算公式基础上,引入水流流速的动能效应。假设河流内水流量相等,建立流速同河流宽度的简单关系,估算了一些调查断面的冰下平均流速;用地表温度资料,对干流域内缺少气象资料的调查断面,在证明结冰期间属于同一天气系统的前提下,用距离平方反比法进行空间插值。最后获得松花江干流河冰厚度统计关系式。用计算的哈尔滨至同江河冰厚度与有限的实测数据比较,发现该方法能够体现人为调节流速对冰生长速率的影响,对计算长距离河冰厚度具有一定精度。     

A hydrological simulation of the water regime in two playa lakes located in southern Spain

The subject of this paper is the detailed hydrological simulation of two playa lakes located in southern Spain from January 2011 to March 2012 on a daily basis. These playas are placed over a 400-km ² shallow aquifer, which is exposed to an increasing stress caused by agricultural activities, mainly olive grove plantations. The objective of the paper is to elaborate a detailed numeric model that simulates the water regime of each playa lake on a daily scale. The simulation is compared to measured water level (WL) data of the playas in order to characterize the groundwater–surface interactions. The ultimate objective of this paper is to assess the environmental impact of the increasing anthropogenic water consumption within the area of research. The results of the GW–surface interaction were very consistent with previous works. One of the playa lakes is groundwater-dependent and the other one is presumably a perched playa lake. The GW discharge of the former playa (214 mm) during the research period stands in sharp contrast to no regional GW discharge in the latter. Water level data prove that the hydrological year (2011–2012) had a very negative water budget. The evapotranspiration estimation was almost as high as double the sum of the precipitation, the run-off, and the groundwater discharge. The simulation of an anthropologically altered water regime proves that water retrieval has a harmful impact on the WL of the playa lakes as well as on the aquifer.     

基于生态流量阈值的河流水文健康演变定量归因

环境变化改变了河流水文情势,影响了河流的生态系统健康,亟需开展变化环境下河流水文健康演变定量归因方法研究。选取北方半干旱地区老哈河流域为研究区,依据流域内3个水文站、17个雨量站和6个气象站1964—2016年数据,基于可变下渗容量模型还原河流的天然流量序列;采用概率密度法计算河流生态流量,基于生态流量阈值推求河流水文健康等级;基于"观测-模拟"对比分析法,定量分离气候变化和人类活动对河流水文健康情势的影响。结果表明:人类活动是甸子和太平庄子流域自1980年以来河流水文健康情势退化的主要原因,其贡献率分别为86.9%和87.9%;大面积农业灌溉用水引起地表径流下降以及水利工程改变天然水文情势,影响了河流水文健康情势;90年代降水量较为充沛,研究流域受人类活动影响程度较小,河流水文健康等级维持在较高的水平。综合生态流量阈值和"观测-模拟"对比分析方法可定量识别河流水文健康情势演变原因,为适应环境变化的河流健康管理提供科学依据。     

多元统计法在河水主要离子含量变化特征及来源分析中的运用——以梧州水文站控制断面为例

文章利用2011年4月到2012年3月对梧州水文站控制断面进行的定期采样数据,分析了该断面河水中主要阴、阳离子的化学组成,并运用多元统计分析方法研究和探讨了河水化学组成变化特征。结果表明,梧州水文站控制断面河水水化学类型以Ca2+ + HCO3-型为主,Na+、Ca2+、Mg2+、HCO3-、SO42-、NO3- 主要来源于岩石的风化,K+ 、Cl-来自于人类活动的输入;河水中离子化学组成受水—岩作用和土壤表面离子交换作用影响,对河水溶质的贡献率分别为69.34％、17.10％。