Yunzhong Jiang

Relationship between the hydrological conditions and the distribution of vegetation communities within the Poyang Lake National Nature Reserve, China

Hydrological characteristics have been recognized as major driving forces for wetland vegetation. The water cycle and hydrological processes of wetland are increasingly influenced by the ongoing climate change and more intensive human activities, which may in turn affect the distribution and structure of vegetation communities. Poyang Lake, located on the south bank of the lower reach of Yangtze River, receives inflows from five tributaries and discharges to the Yangtze River. The unique hydrological conditions of the Poyang Lake wetland create abundant wetland vegetation communities. As a major national hydraulic project, the Three Gorges Dam across the Yangtze River has changed the water regime of Poyang Lake and hence may affect the vegetation distribution. This work aims to investigate the influences of hydrological properties on vegetation structure at broad spatial and temporal scales. Histograms and sensitivity index are used to link the hydrological processes with the vegetation distribution across the Poyang Lake National Nature Reserve. The results show that different vegetation communities react differently to the hydrological conditions. Specifically, certain communities, e.g. Carex and Eremochloa ophiuroides, are able to survive a wide variety of mean water depth and percent time inundated, while others, like Carex–Polygonum criopolitanum, are found to be relatively sensitive to hydrological conditions. It is suggested that this work provides a new insight for evaluating the impact of hydro-engineering projects on vegetation communities and wetland vegetation restoration.

An adaptive particle swarm optimization algorithm for reservoir operation optimization

Reservoir operation optimization (ROO) is a complicated dynamically constrained nonlinear problem that is important in the context of reservoir system operation. In this study, improved adaptive particle swarm optimization (IAPSO) is proposed to solve the problem, which involves many conflicting objectives and constraints. The proposed algorithm takes particle swarm optimization (PSO) as the main evolution method. To overcome the premature convergence of PSO, adjusting dynamically the two sensitive parameters of PSO guides the evolution direction of each particle in the evolution process. In the IAPSO method, an adaptive dynamic parameter control mechanism is applied to determine parameter settings. Moreover, a new strategy is proposed to handle the reservoir output constraint of ROO problem. Finally, the feasibility and effectiveness of the proposed IAPSO algorithm are validated by the Three Gorges Project (TGP) with 42.23bkW power generation and XiLuoDo Project (XLDP) with 30.10bkW. Compared with other methods, the IAPSO provides a better operational result with greater effectiveness and robustness, and appears to be better in terms of power generation benefit and convergence performance. Meanwhile, the optimal results could meet output constraint at each interval.

Use of parallel deterministic dynamic programming and hierarchical adaptive genetic algorithm for reservoir operation optimization

Reservoir operation optimization (ROO) is a complicated dynamically constrained nonlinear problem that is important in the context of reservoir system operation. In this study, parallel deterministic dynamic programming (PDDP) and a hierarchical adaptive genetic algorithm (HAGA) are proposed to solve the problem, which involves many conflicting objectives and constraints. In the PDDP method, multi-threads are found to exhibit better speed-up than single threads and to perform well for up to four threads. In the HAGA, an adaptive dynamic parameter control mechanism is applied to determine parameter settings, and an elite individual is preserved in the archive from the first hierarchy to the second hierarchy. Compared with other methods, the HAGA provides a better operational result with greater effectiveness and robustness because of the population diversity created by the archive operator. Comparison of the results of the HAGA and PDDP shows two contradictory objectives in the ROO problem-economy and reliability. The simulation results reveal that: compared with proposed PDDP, the proposed HAGA integrated with parallel model appears to be better in terms of power generation benefit and computational efficiency.

Flood simulation using parallel genetic algorithm integrated wavelet neural networks

The conventional means of flood simulation and prediction using conceptual hydrological model or artificial neural network (ANN) has provided promising results in recent years. However, it is usually difficult to obtain ideal flood reproducing due to the structure of hydrological model. Back propagation (BP) algorithm of ANN may also reach local optimum when training nodal weights. To improve the mapping capability of neural networks, wavelet function was adopted (WANN) to strengthen the non-linear simulation accuracy and generality. In addition, genetic algorithm is integrated with WANN (GAWANN) to avoid reaching local optimum. Meanwhile, Message Passing Interface (MPI) subroutines are introduced for distributed implement considering the time consumption during nodal weights training. The GAWANN was applied in the flood simulation and prediction in arid area. The test results of 4 independent cases were compared to reveal the relations between historical rainfall and runoff under different time lags. The simulation was also carried out with Xinanjiang model to demonstrate the capability of GAWANN. The numerical experiments in this paper indicated that the parallel GAWANN has strong capability of rain-runoff mapping as well as computational efficiency and is suitable for applications of flood simulation in arid areas.

Development of efficient and cost-effective distributed hydrological modeling tool MWEasyDHM based on open-source MapWindow GIS

Abstract Many regions are still threatened with frequent floods and water resource shortage problems in China. Consequently, the task of reproducing and predicting the hydrological process in watersheds is hard and unavoidable for reducing the risks of damage and loss. Thus, it is necessary to develop an efficient and cost-effective hydrological tool in China as many areas should be modeled. Currently, developed hydrological tools such as Mike SHE and ArcSWAT (soil and water assessment tool based on ArcGIS) show significant power in improving the precision of hydrological modeling in China by considering spatial variability both in land cover and in soil type. However, adopting developed commercial tools in such a large developing country comes at a high cost. Commercial modeling tools usually contain large numbers of formulas, complicated data formats, and many preprocessing or postprocessing steps that may make it difficult for the user to carry out simulation, thus lowering the efficiency of the modeling process. Besides, commercial hydrological models usually cannot be modified or improved to be suitable for some special hydrological conditions in China. Some other hydrological models are open source, but integrated into commercial GIS systems. Therefore, by integrating hydrological simulation code EasyDHM, a hydrological simulation tool named MWEasyDHM was developed based on open-source MapWindow GIS, the purpose of which is to establish the first open-source GIS-based distributed hydrological model tool in China by integrating modules of preprocessing, model computation, parameter estimation, result display, and analysis. MWEasyDHM provides users with a friendly manipulating MapWindow GIS interface, selectable multifunctional hydrological processing modules, and, more importantly, an efficient and cost-effective hydrological simulation tool. The general construction of MWEasyDHM consists of four major parts: (1) a general GIS module for hydrological analysis, (2) a preprocessing module for modeling inputs, (3) a model calibration module, and (4) a postprocessing module. The general GIS module for hydrological analysis is developed on the basis of totally open-source GIS software, MapWindow, which contains basic GIS functions. The preprocessing module is made up of three submodules including a DEM-based submodule for hydrological analysis, a submodule for default parameter calculation, and a submodule for the spatial interpolation of meteorological data. The calibration module contains parallel computation, real-time computation, and visualization. The postprocessing module includes model calibration and model results spatial visualization using tabular form and spatial grids. MWEasyDHM makes it possible for efficient modeling and calibration of EasyDHM, and promises further development of cost-effective applications in various watersheds.

Monthly spatial distributed water resources assessment: a case study

Water resource conservation is of utmost importance, especially for agriculture in developing countries. Frequent occurrences of water shortage have driven more social efforts in researching on water resources spatial distribution, as the land cover changes recently have shown positive influences. For the purpose of efficient water resources management, hydrological processes under different types of land covers and soil textures are supposed to be accurately analyzed and evaluated. Recently developed distributed hydrological mode (DHM) has been a strong hydro-cycle simulation tool for inferring variability and heterogeneity of water resources distribution. In this paper, a spatially distributed Water and Energy Transfer between Soil, Plants and Atmosphere under quasi Steady State (WetSpass) model was introduced in the distributed hydro-cycle simulation on upstream Han river basin. The simulation time-step of WetSpass model was modified from originally one season to currently one month. In addition, an experiential non-linear routing algorithm was integrated into WetSpass for discharge confluence. The study area was delineated into 12 upstream to downstream routing related catchments whose land covers and soil textures were investigated and illustrated. Model verification was completed through the calibration of simulated hydrograph against observation using eleven years of continuous precipitation and meteorological data. Moreover, four criteria were used to evaluate the model performance and the calibrated results of routing parameters were discussed. Furthermore, the distribution of surface runoff generation, evapotranspiration and groundwater recharge were illustrated and analyzed considering the spatial heterogeneity of land cover and soil texture. Results showed that water resource spatial distribution and hydrological processes were closely related to land cover and soil texture and the model had achieved a success in hydro-cycle modeling of upstream Han river basin.

Development and Application of a Distributed Hydrological Model: EasyDHM

AbstractDistributed hydrological models have been commonly used in research involving water management because of their consideration of spatial variability. However, practical applications still encounter technical challenges such as complicated modeling, low computational efficiency, and parameter equifinality. A user-friendly model, EasyDHM, was developed and was shown effective over the years. In this paper, the essential parts of this model, namely, discretization of the spatial units, preparation and initiation of data and parameters, and the main physical processes are briefly introduced. In particular, the roles of the parameter sensitivity analysis and optimization for this model, which have considerably improved the prediction accuracy, are highlighted in this study. From the application to the upstream basin of Han River in China, the simulation and parameter estimation by EasyDHM turned out to be effective and easy to operate. EasyDHM can, therefore, be widely used for practical water manageme...

Development of a flood forecasting system and its application to upper reaches of Zhangweihe River Basin

With changes of underlying surface in Zhangwei River Basin in recent years, it is necessary to build distributed flood forecasting model in upper stream of Zhangwei River Basin to study the hydrologic processes, which can also provide technical support for the flood control department. Based on the physically characterized distributed hydrological model - EasyDHM - a more generalized and expandable method, a flood forecasting system (FFS) has been developed that is equipped with updated modules for pre-processing and automatic parameter optimizing. The general functions of FFS consists of three major parts:(1) a preprocessing module for hydrological analysis and modeling inputs, (2) a model calculation module, and (3) a results analysis module. With its application in the upper reaches of Zhangwei River Basin, this system exhibited a satisfactory performance so that it can provide more information for flood control and dispatch.

Rainfall-Runoff Simulation Using Simulated Annealing Wavelet BP Neural Networks

Wavelet neural network is a powerful tool for rainfall-runoff (RR) prediction. In this essay, a neural network based on wavelet function was proposed. But due to the probability of reaching local minimum of WNN, an improved simulated annealing neural network SAWNN was used in comparison of the WNN, the SAWNN has the ability of reaching the global minimum by employing the disturbing function and is able to mapping non-linear relations. Results show that the SAWNN has ideal performance in RR simulation and has small training error. It also indicates that the training samples should contain as much samples in different condition as possible.

A Novel Optimization Method for Multi-Reservoir Operation Policy Derivation in Complex Inter-Basin Water Transfer System

Joint operation of multiple reservoir system in inter-basin water transfer-supply project is a complex problem because of the complicated structure and cooperated operation policy. The combination of high-dimensional, multi-peak and multiple constraints makes it incredibly difficult to obtain the optimal rule curves for multi-reservoir operation. In view of this, we constructed a joint optimization operation model, considering both water supply and transfer, and proposed the concept of “shape constraints”. To obtain the solution of this high-dimensional optimization model, a novel progressive optimum seeking method, namely Progressive Reservoir Algorithm-Particle Swarm Optimization (PRA-PSO), is presented based on the nature of progressive optimization algorithm (POA) and standard particle swarm optimization (PSO). The water transfer project in northeast China, consisting of three routes eight reservoirs, is selected as a case study. The results show that (1) PRA-PSO is yielding much more promising results when compared with other optimization techniques; (2) shape constraints would narrow the scope of feasible solution area but increase the convergence of algorithm; (3) because of the strong interaction between water transfer and water supply action, the progressive setting of PRA-PSO should be in accordance with the order of reservoir water transfer. The case study indicates the novel optimization method could effectively increase the chance of jumping out of local optimal points, thereby searching for better solutions.