A Study on Grid Based Distributed Rainfall Runoff Models

Two distributed rainfall-runoff models were developed separately by using linear and nonlinear storage approaches for simulating the heterogeneity of hydrological processes over the catchment. A 1 × 1 km grid-based mesh was used to abstract the geometry of the catchment. The hydrological processes and geographic information were modeled on this scale. Both linear and nonlinear models were calibrated by global optimization technique. The models to simulate spatial hydrological processes over a catchment were verified using the observed hydrographs at two stream gauged stations within the catchment. The nonlinear model has better performance than the linear model for two verification storm events.     

分布式水文概念性模型及应用

在遥感与GIS支持下,建立地理空间信息库,提取了流域土地利用、土壤类型和植被类型等地理信息及相应的水空间参数,采用已有的水概念性模型,建立了一个分布式水概念性模型．模型结构简单,所需参数较少,易于率定,可操作性强．实例应用表明,该模型对雁栖河流域径流量的模拟是有效的,可用于评估流域水资源量、气候变化以及土地利用变化对水资源的影响．     

重要水源地小流域水环境动态模拟及调控研究

本研究选取北京密云水库上游曹家路小流域为对象,通过野外监测和模型计算的方法对小流域水环境进行动态模拟及调控研究。综合运用水文学、水环境学、数理统计和地理信息系统等方法,并结合野外监测、实验室分析和计算机模拟等手段,建立了小流域半分布式水文模型和一维河道水质模型。运用该模型对曹家路小流域的水质状况进行了模拟计算,得到了流域出口断面NH3-N、Os、BOD、COD和TN等水质因子的总体特征和全年全时段变化过程。根据1956~2000年的水文数据,分析了流域特征水文年水环境的动态变化,提出了相应的水质保护和水环境容量利用综合调控方案,并依据区域的经济发展进行了水环境动态规划。     

Flood Modeling for Complex Terrain Using GIS and Remote Sensed Information

A spatially distributed hydrological model WetSpa (Water and Energy Transfer between Soil, Plants and Atmosphere) working on an hourly time scale is presented in this paper. The model combines elevation, soil and land use data, and predicts flood hydrograph and the spatial distribution of hydrological characteristics in a watershed. The model is tested on a small catchment in Belgium for which topography and soil data are available in GIS form, while the land use and soil cover is obtained from remote sensed images. The resulting calculated discharges compare favorably with the field measurements. Next a 102-year series of measured hourly precipitation data is processed with the model and the resulting hydrographs are analyzed statistically to determine the characteristics of extreme floods. Finally, the simulated extreme peak discharges are compared to the results calculated with design storms. Comparison of the two methods shows that the model is capable to predict both normal and extreme floods. Since the model accounts for spatially distributed hydrological and geophysical characteristics of the catchment, it is suitable for simulating hydrological processes in a complex terrain and for predicting the influence of changes in land use on the hydrological behavior of a river basin.     

A Genetic Programming Approach to System Identification of Rainfall-Runoff Models

Advancements in data acquisition, storage and retrieval are progressing at an extraordinary rate, whereas the same in the field of knowledge extraction from data is yet to be accomplished. The challenges associated with hydrological datasets, including complexity, non-linearity and multicollinearity, motivate the use of machine learning to build hydrological models. Increasing global climate change and urbanization call for better understanding of altered rainfall-runoff processes. There is a requirement that models are intelligible estimates of underlying physics, coupling explanatory and predictive components, maintaining parsimony and accuracy. Genetic Programming, an evolutionary computation technique has been used for short-term prediction and forecast in the field of hydrology. Advancing data science in hydrology can be achieved by tapping the full potential of GP in defining an evolutionary flexible modelling framework that balances prior information, simulation accuracy and strategy for future uncertainty. As a preliminary step, GP is used in conjunction with a conceptual rainfall-runoff model to solve model configuration problem. Two datasets belonging to a tropical catchment of Singapore and a temperate catchment of South Island, New Zealand with contrasting characteristics are analyzed in this study. The results indicate that proposed approach successfully combines the merits of evolutionary algorithm and conceptual knowledge in the generation of optimal model structure and associated parameters to capture runoff dynamics of catchments.     

Hydrological Simulation by SWAT Model with Fixed and Varied Parameterization Approaches Under Land Use Change

Land use and land cover (LULC) change within a watershed is recognized as an important factor affecting hydrological processes and water resources. Modeling the hydrological effects of land-use change is important not only for after-the-fact analyses, but also for understanding and predicting the potential hydrological consequences of existing land-use practices. The main aim of the study is to understand and quantify the hydrological processes in a rapid urbanization region. The SWAT model and the Qinhuai River basin, one of the most rapidly urbanizing regions in China were selected to perform the study. In the study, a varied parameterization strategy was developed by establishing regression equations with selected SWAT parameters as dependent variables and catchment impermeable area as independent variable. The performance of the newly developed varied parameterization approach was compared with the conventional fixed parameterization approach in simulating the hydrological processes under LULC changes. The results showed that the model simulation with varied parameterization approach has a large improvement over the conventional fixed parameterization approach in terms of both long-term water balance and flood events simulations. The proposed modeling approach could provide an essential reference for the study of assessing the impact of LULC changes on hydrology in other regions.     

三地理信息系统中的水文数据模型研究与探讨

地理信息系统（GIS）中的水文数据模型是GIS在水文水资源应用中的核心和基础。结合GIS在水文水资源中应用的现状与需求,分析和总结了2种GIS水文数据模型;从构造GIS水文地理空间数据库的角度出发,对与水文现象相关的各种地理特征进行深刻认识和理解,在此基础上提出了面向对象的GIS水文数据模型设计的结构和要点。     

水文模型植被参数获取方法及应用研究

引入Spot/Vegetation(简称SPOT-VGT)归一化植被指数NDVI遥感资料,建立了叶面积指数LAI-NDVI模型,进行大尺度陆面水文模型VIC植被参数获取方法研究,将结果应用于黑河莺落峡流域水文模拟,并分析了植被参数对陆面水文循环要素的影响.结果表明:采用SPOT-VGT遥感资料建立的LAI-NDVI模型计算的叶面积指数较好地反映了实际叶面积指数的空间分布和时间变化,用此方法获取的植被参数结果优于模型推荐的查表法.     

流域水文过程与植被相互作用研究评述

从流域水文过程与植被相互作用规律、流域生态水文模型、流域生态水文对气候变化的响应三个方面，对国内外相关研究现状进行了总结分析。研究发现，当前流域水文学正在从以单一水循环过程为主要研究对象发展成以研究水分、能量与物质耦合循环以及水文过程与生态过程的相互作用等为主要内容的综合性和交叉性学科。现关于流域水文过程与植被之间的关系研究多集中于单向作用的研究，如水文过程对植被的影响研究和植被变化对水文过程的影响研究，而对水文过程与植被之间的反馈机制以及对流域内土壤-植被-大气复杂系统的整体研究不足，缺乏对流域水文过程与植被相互作用机理的全面认识。研究表明气候变化已经影响到流域水文过程和植被生长，气候变化下的流域生态水文响应是水文学研究的前沿课题。水文学需要强化对流域生态水文机理的研究，只有在充分揭示流域生态水文机理的前提下，才能预测未来气候变化下的流域生态水文响应。生态最优性原理能够解释植被对外界环境变化的响应，从而被应用于描述植被与水文过程的相互作用。基于生态最优性原理的流域生态水文模型已逐渐成为生态水文学的研究热点之一。     

融雪的水量平衡模型在内蒙古锡林河流域水文模拟中的应用

水量平衡模型是目前水文及环境分析中最常用的工具和手段之一,半干旱地区的水文模拟是目前水文科学研究中的难点.以内蒙古地区的锡林河流域为研究对象,开展了考虑融雪的水量平衡模型(Snowmelt-based Water Balance Model,SWBM模型)的拓展性应用研究.结果表明:锡林河流域气候干旱,产流受降水和融雪驱动,流域降水量及实测径流量均呈现弱减少趋势.SWBM模型对对月径流过程具有较好的模拟效果,率定期和检验期的模型效率系数均可超过60％,相对误差小于8％,说明该模型可以用于研究气候变化对半干旱地区的影响评价.     

基于SVAT模型的喀斯特地区水文过程尺度效应研究

水文模型尺度效应是水文学研究的前沿问题,为深入探索水文模型的空间尺度效应,本文采用耦合遥感数据的 SVAT 模型,分别在研究区—区县单元—小流域三个不同量级的空间尺度,基于蓝水绿水视角,对贵阳市非城镇地区的水文变化过程进行模拟,结果表明：在降水量保持不变的情况下,随着植被覆盖度的不断增加,三个不同空间尺度的生态绿水量均呈线性增长趋势;渗漏量在区县和小流域空间尺度,产生了少量异常值,但均为小数点第三位之后的微小波动;水文变化趋势总体上表现出良好的一致性;SVAT 模型对研究区水文变化过程的模拟,尺度效应影响较为有限。     

基于数字地形信息的拉萨河流域河宽预测模型研究

河道宽度是重要的水文特征,对水文计算具有重要意义。以拉萨河流域为研究区,依据Google Earth影像,测量了1 000个河段的河宽,计算了相应测段的集水面积、局部坡度、坡度原点矩、河道曲率4项地形要素。使用其中800个河段的数据判别河宽与各地形要素的相关关系,选取与河宽相关性最好的集水面积和坡度原点矩两要素,构建了集水面积模型、坡度原点矩模型及4种河宽因子模型,使用另外200个河段的数据进行模型验证。结果表明：在集水面积小于2 100 km²的拉萨河上游河段,基于集水面积和坡度原点矩的河宽因子模型效果最优,在集水面积大于2 100 km²的拉萨河下游河段,基于集水面积的模型效果最优。因此,预测拉萨河流域河宽时应以2 100 km²集水面积为阈值,在上游使用河宽因子模型,在下游使用集水面积模型,采用该方法预测的上、下游河宽误差均小于20%。     

Temporal and spatial variations of runoff composition revealed by isotopic signals in Nianchu River catchment,Tibet

Understanding the hydrology of glaciated catchments is an important step in assessing the vulnerability of water resources to a changing climate. Based on multi-isotopes of water (²H, ¹⁸O and ³H) and dissolved radon (²²²Rn), the temporal and spatial variabilities of major hydrological processes along the main flow and tributaries in the Nianchu River catchment were examined and the isotopic response to climate variation was identified. Geographic variation in changes of isotopic composition that differ from other rivers in the Nianchu River catchment was apparent. Along the direction of runoff, river δ¹⁸O exhibited more depletion, which was closely related to water mixing and groundwater discharge. End-member mixing analysis using isotopic tracers suggested that annual recharge from summer rainfall and glacial meltwater maintained the surface water resources (their respective contributions rate were 65.9% and 26.5%); groundwater had a significant contribution on runoff in the dry season (about 46.6%). Summer rainfall and meltwater rapidly infiltrated through a series of faults and fissures and were, stored in underground reservoirs and released to runoff in the dry season, thereby ensuring rapid circulation and renewal of water resources (annual renewal proportion was about 40%). It was concluded that rainfall infiltration, meltwater and groundwater storage play important roles in the hydrology of this alpine-cold catchment. Similar to a general alpine-cold catchment, the stable isotopes (δ²H, δ¹⁸O) of river runoff will gradually be enriched, while groundwater reserves will increase in the Nianchu River catchment as a result of climate warming and an acceleration of glacial-melting.     

Developing an independent, generic, phosphorus modelling component for use with grid-oriented, physically based distributed catchment models.

Grid-oriented, physically based catchment models calculate fields of various hydrological variables relevant to phosphorus detachment and transport. These include (i) for surface transport: overland flow depth and flow in the coordinate directions, sediment load, and sediment concentration and (ii) for subsurface transport: soil moisture and hydraulic head at various depths in the soil. These variables can be considered as decoupled from any chemical phosphorus model since phosphorus concentrations, either as dissolved or particulate, do not influence the model calculations of the hydrological fields. Thus the phosphorus concentration calculations can be carried out independently from and after the hydrological calculations. This makes it possible to produce a separate phosphorus modelling component which takes as input the hydrological fields produced by the catchment model and which calculates, at each simulation time step, the phosphorus concentrations in the flows. This paper summarises the equations and structure of such a Grid Oriented Phosphorus Component (GOPC) developed by the authors for simulating phosphorus concentrations and loads using the outputs of a fully distributed physical based hydrological model. The GOPC performance is illustrated by an example of a simplified hypothetical catchment subjected to some ideal conditions.     

Streamflow Modeling in a Highly Managed Mountainous Glacier Watershed Using SWAT: The Upper Rhone River Watershed Case in Switzerland

Streamflow simulation is often challenging in mountainous watersheds because of irregular topography and complex hydrological processes. Rates of change in precipitation and temperature with respect to elevation often limit the ability to reproduce stream runoff by hydrological models. Anthropogenic influence, such as water transfers in high altitude hydropower reservoirs increases the difficulty in modeling since the natural flow regime is altered by long term storage of water in the reservoirs. The Soil and Water Assessment Tool (SWAT) was used for simulating streamflow in the upper Rhone watershed located in the south western part of Switzerland. The catchment area covers 5220 km², where most of the land cover is dominated by forest and 14 % is glacier. Streamflow calibration was done at daily time steps for the period of 2001–2005, and validated for 2006–2010. Two different approaches were used for simulating snow and glacier melt process, namely the temperature index approach with and without elevation bands. The hydropower network was implemented based on the intake points that form part of the inter-reservoir network. Subbasins were grouped into two major categories with glaciers and without glaciers for simulating snow and glacier melt processes. Model performance was evaluated both visually and statistically where a good relation between observed and simulated discharge was found. Our study suggests that a proper configuration of the network leads to better model performance despite the complexity that arises for water transaction. Implementing elevation bands generates better results than without elevation bands. Results show that considering all the complexity arising from natural variability and anthropogenic influences, SWAT performs well in simulating runoff in the upper Rhone watershed. Findings from this study can be applicable for high elevation snow and glacier dominated catchments with similar hydro-physiographic constraints.     

Small Catchment Agricultural Management Using Decision Variables Defined at Catchment Scale and a Fuzzy Rule-Based System: A Mediterranean Vineyard Case Study

Physically based hydrological models are increasingly used to simulate the impact of land use changes on water and mass transfers. The problems associated with this type of parameter-rich model from a water management perspective are related to the need for (1) a large number of local parameters instead of only a few catchment-scale decision variables and (2) the technical skills and computational expertise necessary to perform these models. This study aimed to show that it is possible to define a reduced number of decision variables and rules to synthesise numerical simulations carried out through a physically based model. The MHYDAS model was run on a Mediterranean vineyard catchment located in southern France (Roujan, Herault) for an actual, common rainfall event to calculate the runoff coefficient. The simulation results concerned 3,000 samples of contrasted scenarios. The scenarios were characterised by four catchment-scale decision variables related to agricultural practices: the proportion of the area of non agricultural land, the proportion of the area subjected to full chemical weeding practices (with the complement being mechanical weeding), the spatial arrangement of the practices based on the distance to the outlet and the initial soil moisture content. The simulation results were used to generate fuzzy linguistic rules to predict the runoff coefficient, as computed by the physical model from the decision variables. For a common end of spring rainfall event, simulations showed that the runoff coefficient was most heavily influenced by the initial soil moisture and the proportion of the area of full chemical weeding practices and the proportion of the area of other land uses and their spatial arrangement also played a role. The fuzzy rule-based model was able to reproduce the hydrological output with good accuracy (R² = 0.97). Sensitivity analysis to the rainfall magnitude showed that if the amount of rainfall was the key factor explaining the runoff coefficient absolute values, the structure of the rule base remained stable for rainfall events close to the one studied.     

Development of a distributed hydrological model based on urban databanks--production processes of URBS.

The objective of this study is to present a distributed hydrological model especially dedicated to urban catchments, and able to represent hydrological processes usually neglected in urban modelling, such as evapotranspiration, infiltration in roads, or direct infiltration of soil water in sewers. This model, called URBS (as Urban Runoff Branching Structure) is distributed considering the spatial variability of land use which is well known thanks to urban databanks managed by GIS. The production function is detailed at each cadastral parcel scale, and the runoff produced is routed by a simple transfer function. The estimation of the input parameters of the model is mostly based on physical considerations, and the model is applied on a suburban catchment in Nantes (France) in order to evaluate the interest of the distribution of the hydrological variables.     

Management Options to Improve Water Quality in Lake Peipsi: Insights from Large Scale Models and Remote Sensing

Nutrient pollution causes frequent blooms of potentially harmful cyanobacteria in Lake Peipsi (Estonia/Russia). Although external nutrient loading has reduced since the 1990s, lake water quality has barely improved, and eutrophication is still considered a threat to lake biota and water usage. To understand the recovery dynamics of the lake it is necessary to analyse the effects of land use and lake management on water quality to develop mitigation strategies. Comprehensive analysis has thus far failed due to information gaps inherent to conventional monitoring strategies. We show how two large-scale hydrological models using Earth observation data provide spatial information on pollution and can help explain the causes of past and current lake eutrophication. WaterGAP3.2 provides valid estimates of present and probable future phosphorus concentration in the lake water, based on past hydrological conditions. WaterWorld models spatial potential water quality and a scenario of optimal pollution reduction. Remotely sensed optical water quality data can be used to analyse recent, spatial water quality dynamics. The spatial and temporal algae distributions and can help explain eutrophication causes at Lake Peipsi and its catchment, adding value to in situ monitoring and supporting river basin management with large scale data.