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1.
Interest in semiarid climate forecasting has prominently grown due to risks associated with above average levels of precipitation amount. Longer-lead forecasts in semiarid watersheds are difficult to make due to short-term extremes and data scarcity. The current research is a new application of classification and regression trees (CART) model, which is rule-based algorithm, for prediction of the precipitation over a highly complex semiarid climate system using climate signals. We also aimed to compare the accuracy of the CART model with two most commonly applied models including time series modeling (ARIMA), and adaptive neuro-fuzzy inference system (ANFIS) for prediction of the precipitation. Various combinations of large-scale climate signals were considered as inputs. The results indicated that the CART model had a better results (with Nash–Sutcliffe efficiency, NSE?>?0.75) compared to the ANFIS and ARIMA in forecasting precipitation. Also, the results demonstrated that the ANFIS method can predict the precipitation values more accurately than the time series model based on various performance criteria. Further, fall forecasts ranked “very good” for the CART method, while the ANFIS and the time series model approximately indicated “satisfactory” and “unsatisfactory” performances for all stations, respectively. The forecasts from the CART approach can be helpful and critical for decision makers when precipitation forecast heralds a prolonged drought or flash flood.  相似文献   

2.
High turbid water in the river has been one of the major concerns to the downstream residence. During heavy local rainfall, high turbid water occurs in many countries located in the Asian monsoon climate region. The Andong and the Imha reservoir, two adjacent multipurpose dams, located in the upstream of the Nakdong River in Korea have suffered from severe turbid water problem. This study applied hydrodynamic water quality model CE-Qual-Riv1 to simulate turbidity propagation in downstream coupled with long-term watershed hydrologic model SWAT to consider contributions of tributaries. The outputs of runoff and suspended sediment in tributaries are incorporated into the input data necessary for the hydrodynamic water quality model. The simulation focused on the joint dam operation to minimize the negative impact of high turbid water in downstream river. Simulated turbidity in downstream shows a good agreement with the observed data, and the approach proposed in this study is applicable for establishing a sound turbid water management in downstream of the reservoir.  相似文献   

3.
The complex nature of hydrological phenomena, like rainfall and river flow, causes some limitations for some admired soft computing models in order to predict the phenomenon. Evolutionary algorithms (EA) are novel methods that used to cover the weaknesses of the classic training algorithms, such as trapping in local optima, poor performance in networks with large parameters, over-fitting, and etc. In this study, some evolutionary algorithms, including genetic algorithm (GA), ant colony optimization for continuous domain (ACOR), and particle swarm optimization (PSO), have been used to train adaptive neuro-fuzzy inference system (ANFIS) in order to predict river flow. For this purpose, classic and hybrid ANFIS models were trained using river flow data obtained from upstream stations to predict 1-, 3-, 5-, and 7-day ahead river flow of downstream station. The best inputs were selected using correlation coefficient and a sensitivity analysis test (cosine amplitude). The results showed that PSO improved the performance of classic ANFIS in all the periods such that the averages of coefficient of determination, R2, root mean square error, RMSE (m3/s), mean absolute relative error, MARE, and Nash-Sutcliffe efficiency coefficient (NSE) were improved up to 0.19, 0.30, 43.8, and 0.13%, respectively. Classic ANFIS was only capable to predict river flow in 1-day ahead while EA improved this ability to 5-day ahead. Cosine amplitude method was recognized as an appropriate sensitivity analysis method in order to select the best inputs.  相似文献   

4.
Performance of a hybrid assimilation system combining 3D Var based NGFS (NCMRWF Global Forecast System) with ETR (Ensemble Transform with Rescaling) based Global Ensemble Forecast (GEFS) of resolution T-190L28 is investigated. The experiment is conducted for a period of one week in June 2013 and forecast skills over different spatial domains are compared with respect to mean analysis state. Rainfall forecast is verified over Indian region against combined observations of IMD and NCMRWF. Hybrid assimilation produced marginal improvements in overall forecast skill in comparison with 3D Var. Hybrid experiment made significant improvement in wind forecasts in all the regions on verification against mean analysis. The verification of forecasts with radiosonde observations also show improvement in wind forecasts with the hybrid assimilation. On verification against observations, hybrid experiment shows more improvement in temperature and wind forecasts at upper levels. Both hybrid and operational 3D Var failed in prediction of extreme rainfall event over Uttarakhand on 17 June, 2013.  相似文献   

5.
The January 2010 earthquake that devastated Haiti left its population ever more vulnerable to rainfall-induced flash floods. A flash flood guidance system has been implemented to provide real-time information on the potential of small (~70 km2) basins for flash flooding throughout Haiti. This system has components for satellite rainfall ingest and adjustment on the basis of rain gauge information, dynamic soil water deficit estimation, ingest of operational mesoscale model quantitative precipitation forecasts, and estimation of the times of channel flow at bankfull. The result of the system integration is the estimation of the flash flood guidance (FFG) for a given basin and for a given duration. FFG is the amount of rain of a given duration over a small basin that causes minor flooding in the outlet of the basin. Amounts predicted or nowcasted that are higher than the FFG indicate basins with potential for flash flooding. In preparation for Hurricane Tomas’ landfall in early November 2010, the FFG system was used to generate 36-h forecasts of flash flood occurrence based on rainfall forecasts of the nested high-resolution North American Model of the National Centers for Environmental Prediction. Assessment of the forecast flood maps and forecast precipitation indicates the utility and value of the forecasts in understanding the spatial distribution of the expected flooding for mitigation and disaster management. It also highlights the need for explicit uncertainty characterization of forecast risk products due to large uncertainties in quantitative precipitation forecasts on hydrologic basin scales.  相似文献   

6.
In the present study, diagnostic studies were undertaken using station-based rainfall data sets of selected stations of Guyana to understand the variability of rainfall. The multidecadal variation in rainfall of coastal station Georgetown and inland station Timehri has shown that the rainfall variability was less during the May–July (20–30%) of primary wet season compared to the December--January (60–70%) of second wet season. The rainfall analysis of Georgetown based on data series from 1916 to 2007 shows that El Niño/La Niña has direct relation with monthly mean rainfall of Guyana. The impact is more predominant during the second wet season December--January. A high-resolution Weather Research and Forecasting model was made operational to generate real-time forecasts up to 84 h based on 00 UTC global forecast system (GFS), NCEP initial condition. The model real-time rainfall forecast during July 2010 evaluation has shown a reasonable skill of the forecast model in predicting the heavy rainfall events and major circulation features for day-to-day operational forecast guidance. In addition to the operational experimental forecast, as part of model validation, a few sensitivity experiments are also conducted with the combination of two cloud cumulus (Kain--Fritsch (KF) and Betts–Miller–Janjic (BMJ)) and three microphysical schemes (Ferrier et al. WSM-3 simple ice scheme and Lin et al.) for heavy rainfall event occurred during 28–30 May 2010 over coastal Guyana and tropical Hurricane ‘EARL’ formed during 25 August–04 September 2010 over east Caribbean Sea. It was observed that there are major differences in the simulations of heavy rainfall event among the cumulus schemes, in spite of using the same initial and boundary conditions and model configuration. Overall, it was observed that the combination of BMJ and WSM-3 has shown qualitatively close to the observed heavy rainfall event even though the predicted amounts are less. In the case of tropical Hurricane ‘EARL’, the forecast track in all the six experiments based on 00 UTC of 28 August 2010 initial conditions for the forecast up to 84 h has shown that the combination of KF cumulus and Ferrier microphysics scheme has shown less track errors compared to other combinations. The overall average position errors for all the six experiments taken together work out to 103 km in 24, 199 km in 48, 197 km in 72 and 174 km in 84 h.  相似文献   

7.
A nonlinear ensemble prediction model for typhoon rainstorm has been developed based on particle swarm optimization-neural network (PSO-NN). In this model, PSO algorithm is employed for optimizing the network structure and initial weight of the NN with creating multiple ensemble members. The model input of the ensemble member is the high correlated grid point factors selected from the rainfall forecast field of Japan Meteorological Agency numerical prediction products using the stepwise regression method, and the model output is the future 24 h rainfall forecast of the 89 stations. Results show that the objective prediction model is more accurate than the numerical prediction model which is directly interpolated into the stations, so it can better been implemented for the interpretation and application of numerical prediction products, indicating a potentially better operational weather prediction.  相似文献   

8.
The present research was carried out by using artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), cokriging (CK) and ordinary kriging (OK) using the rainfall and streamflow data for suspended sediment load forecasting. For this reason, the time series of daily rainfall (mm), streamflow (m3/s), and suspended sediment load (tons/day) data were used from the Kojor forest watershed near the Caspian Sea between 28 October 2007 and 21 September 2010 (776 days). Root mean square error, efficiency coefficient, mean absolute error, and mean relative error statistics are used for evaluating the accuracy of the ANN, ANFIS, CK, and OK models. In the first part of the study, various combinations of current daily rainfall, streamflow and past daily rainfall, streamflow data are used as inputs to the neural network and neuro-fuzzy computing technique so as to estimate current suspended sediment. Also, the accuracy of the ANN and ANFIS models are compared together in suspended sediment load forecasting. Comparison results reveal that the ANFIS model provided better estimation than the ANN model. In the second part of the study, the ANN and ANFIS models are compared with OK and CK. The comparison results reveal that CK was a better estimation than the OK. The ANFIS and ANN models also provided better estimation than the OK and CK models.  相似文献   

9.
Soil temperature has an important role in agricultural, hydrological, meteorological and climatological studies. In the present research, monthly mean soil temperature at four different depths (5, 10, 50 and 100 cm) was estimated using artificial neural networks (ANN), adaptive neuro-fuzzy inference system (ANFIS) and gene expression programming (GEP). The monthly mean soil temperature data of 31 stations over Iran were employed. In this process, the data of 21 and 10 stations were used for training and testing stages of used models, respectively. Furthermore, the geographical information including latitude, longitude and altitude as well as periodicity component (the number of months) was considered as inputs in the mentioned intelligent models. The results demonstrated that the ANN and ANFIS models had good performance in comparison with the GEP model. Nevertheless, the ANFIS generally performed better than ANN model.  相似文献   

10.
沈倩娜  张霞 《水文》2021,41(2):80-85
2017年6月下旬到7月初,2019年7月上旬到中旬,湘江干流接连发生特大洪水。通过分析湘江流域多个测站的水文整编资料,结合部分实时信息,从降雨过程时空分布、干支流有关测站洪水水位流量过程、洪水组成、洪量、洪水传播时间与宣泄速度等方面,对2017年洪水与2019年洪水的暴雨洪水特征进行了对比分析。2017年洪水,湘潭站上游的衡山、衡阳、冷水滩站水位过程与流量过程对应呈双峰形状,而湘潭站水位过程没有出现双峰;2019年洪水,湘江干流上下游站点的水位过程与流量过程基本对应,均呈双峰形状;2017年洪水宣泄慢,2019年洪水宣泄极快。2017年洪水与2019年洪水流量过程与水位过程起伏不对应、洪水宣泄速度的差异主要是由于洞庭湖水位顶托因素影响导致。  相似文献   

11.
The waters of the Seine river estuary, located in a highly anthropogenicized area in the northern part of France, are of poor microbiological quality; the concentrations of faecal bacteria usually exceed the European Union bathing and recreational water directives. The aim of the present study was to identify the main sources of the faecal pollution of the Seine estuary in order to help define priorities for management and sanitation efforts. Budgets of faecal coliform (FC) inputs to the estuary were established for various hydrological conditions. Main sources of FC were the outfalls of the treated effluents of the wastewater treatment plants (WWTPs) located along the estuary, the faecal bacteria brought in through the tributaries of the Seine estuary, and the faecal bacteria transported by the Seine river flow at the estuary entrance at Poses dam. In order to quantify these inputs, FC were enumerated during sampling campaigns conducted for various hydrological conditions in the Seine at the entrance of the estuary, in the tributaries close to their confluence with the estuary, and in the effluents of some WWTPs located along the estuary. The importance of the flux of FC transported by the Seine river flow at the estuary entrance at Poses dam decreased from 92% of the total FC input when the flow rate was high (717 m3 s−1) to 5% when flow rate was low (143 m3 s−1). The release of the domestic wastewaters of the large city of Paris located 120 km upstream from the entrance of the estuary was mainly responsible for this microbiological pollution. At low flow rates, the tributaries represent the most important source of FC (64–76% for flow rates of the Seine at Poses at approximately 150 m3 s−1), mainly from the Robec and Eure rivers. The treated wastewater of the WWTPs located along the estuary was the second source of FC for low flow conditions (19–30%); it was less important for high to intermediate flow rate conditions.  相似文献   

12.
Farmers?? adaptation to climate change over southern Africa may become an elusive concept if adequate attention is not rendered to the most important adaptive tool, the regional seasonal forecasting system. Uptake of the convectional seasonal rainfall forecasts issued through the southern African regional climate outlook forum process in Zimbabwe is very low, most probably due to an inherent poor forecast skill and inadequate lead time. Zimbabwe??s recurrent droughts are never in forecast, and the bias towards near normal conditions is almost perpetual. Consequently, the forecasts are poorly valued by the farmers as benefits accrued from these forecasts are minimal. The dissemination process is also very complicated, resulting in the late and distorted reception. The probabilistic nature of the forecast renders it difficult to interpret by the farmers, hence the need to review the whole system. An innovative approach to a regional seasonal forecasting system developed through a participatory process so as to offer a practically possible remedial option is described in this paper. The main added advantage over the convectional forecast is that the new forecast system carries with it, predominantly binary forecast information desperately needed by local farmers??whether a drought will occur in a given season. Hence, the tailored forecast is easier for farmers to understand and act on compared to the conventional method of using tercile probabilities. It does not only provide a better forecasting skill, but gives additional indications of the intra-seasonal distribution of the rainfall including onsets, cessations, wet spell and dry spell locations for specific terciles. The lead time is more than 3?months, which is adequate for the farmers to prepare their land well before the onset of the rains. Its simplicity renders it relatively easy to use, with model inputs only requiring the states of El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) climate modes. The developed forecast system could be one way to enhance management of risks and opportunities in rain-fed agriculture among small-holder farmers not only in Zimbabwe but also throughout the SADC region where the impact of ENSO and/or IOD on a desired station rainfall is significant.  相似文献   

13.
During July 11–14, 2012, deadly floods and landslides triggered by a series of unprecedented heavy rains hit Kyushu, Japan, causing at least 32 deaths and around 400,000 evacuations. We focus on synoptic anomalies identified after inspecting rainfall patterns and documenting the conditions associated with this tragic event using data combined from the Global Rainfall Map in Near Real Time data, the NCEP/NCAR Reanalysis dataset, and the global forecast system. Rainfall maps indicated that there were many heavy rains in Kyushu in these days and this disaster was associated with the pattern of forecasts and standardized anomalies. A weather trough with positive height anomalies appeared, the center of which moved to the north of Japan over this period, which might cause wind anomalies and whereby lots of water vapor were transported to Kyushu area with up to 90 m s?1, and high values of precipitable water formed with up to 60 mm. These results suggest that a larger-scale pattern is conducive for heavy rainfall and the anomalies put the pattern in context as to the potential for an extreme rainfall event, which can provide insights and methods for predicting extreme events’ or something similar.  相似文献   

14.
Quantitative precipitation forecasting (QPF) has been attempted over the Narmada Catchment following a statistical approach. The catchment has been divided into five sub-regions for the development of QPF models with a maximum lead-time of 24 hours. For this purpose the data of daily rainfall from 56 raingauge stations, twice daily observations on different surface meteorological parameters from 28 meteorological observatories and upper air data from 11 aerological stations for the nine monsoon seasons of 1972–1980 have been utilized. The horizontal divergence, relative vorticity, vertical velocity and moisture divergence are computed using the kinematic method at different pressure levels and used as independent variables along with the rainfall and surface meteorological parameters. Multiple linear regression equations have been developed using the stepwise procedure separately with actual and square root and log-transformed rainfall using 8-year data (1972–1979). When these equations were verified with an independent data for the monsoon season of 1980, it was found that the transformed rainfall equations fared much better compared to the actual rainfall equations. The performance of the forecasts of QPF model compared to the climatological and persistence forecasts has been assessed by computing the verification scores using the forecasts for the monsoon season of 1980.  相似文献   

15.
牛最荣  陈学林  王学良 《水文》2015,35(5):91-96
白龙江引水工程被列入国家确定的172项重大水利工程项目之一,分析研究白龙江干流代表站径流变化特征并进行未来趋势预测,为实施白龙江引水工程提供技术支撑。对白龙江干流白云、舟曲、武都、碧口4个代表站1956~2013年的实测径流系列资料进行分析,采用周期波均值外延叠加模型、谐波分析模型和逐步回归分析模型组合形成的加法模型对代表站未来径流变化趋势进行分析预测。结果表明:(1)该4站9月份多年平均流量占全年径流量比例最大,主汛期6~9月多年平均流量占全年径流量比例达到50%左右。(2)4个水文站多年径流量变化趋势呈现出逐渐缓慢减少的趋势,上游减少的幅度比下游小。(3)预测2015、2020、2025年年径流量的结果是:白云水文站均小于多年平均值,武都水文站均大于多年均值,舟曲和碧口水文站在多年均值上下浮动。  相似文献   

16.
The Thornthwaite and Mather water budget is a simple and frequently applicable tool to estimate surpluses of water, which are not stored in the soil profile. Combining it with the empiric CN-method of the US Soil Conservation Service (US-SCS), which is applied to daily rainfall records, it is possible to estimate the runoff, and this way, from the difference between surpluses and runoff, to estimate the net infiltration that would recharge a phreatic aquifer. In order to apply both methods during a sequence of years, it is necessary to predict the number of rain events per month, and the rainfall depth for each event. In this work, the author proposes a methodology based on the theorem of Bayes to estimate the number of occurrences of rainy events in a considered month conditioning the forecast to the monthly rainfall. In addition, an exponential distribution to generate rainfall depth knowing the monthly rainfall was done. Both algorithms were applied in four stations of the southern region of Santa Fe province (Argentina). More than 7,600 forecasts of rain occurrences and rainfall depths were compared with the observed records. Moreover, the runoff values estimated by means of the US-SCS method, using the observed rainfall and using rainfalls predicted with the algorithms were also compared. In both cases, the obtained results were also very satisfactory. The proposed methodologies allow the correct application of the balance of Thornthwaite and Mather together with the US-SCS method and a good forecast of monthly runoff and net infiltration.  相似文献   

17.
塔里木河中游滞洪区的形成及其对生态环境的影响   总被引：32，自引：16，他引：16  
塔里木河位于我国新疆内陆干旱区,是我国最大的内陆河,全长1321km.近40a来,在阿克苏河、叶尔羌河、和田河、开都河 孔雀河四条源流出山口天然来水量未减少,且在20世纪90年代增加7%的情况下,由于源流区人类活动的影响和粗放型农业,补给塔里木河水量以年平均2500×104m3的速率减少,加之中游区新生滞洪区耗水严重,进入下游的水量锐减.20世纪70年代以来又被大西海子水库几乎全部拦蓄,导致最下游320km河道断流近30a,地下水位下降,植被衰退,沙漠化进程加快,"绿色走廊"危在旦夕,生态环境恶化,已影响到流域人类的生存安全.  相似文献   

18.
史晓亮  杨志勇  绪正瑞  李颖 《水文》2014,34(6):26-32
降雨输入对分布式流域水文模拟具有重要影响。针对流域降雨资料不完整的情况,以武烈河流域为例,基于反距离加权平均法对雨量站降雨资料进行插补延长,并结合SWAT模型研究了降雨输入不确定性对分布式流域水文模拟的影响。结果表明:不同降雨输入对流域平均降雨量的影响较小,但基于气象站资料的降雨数据在降雨空间差异显著的年份会明显低估面雨量,且在夏季汛期表现更为显著;不同降雨输入对分布式流域水文模拟的影响较大;在雨量站降雨资料不完整的情况下,通过对雨量站降雨数据进行插补延长,相对于直接利用气象站降雨资料,在一定程度上可以提高径流模拟精度,满足降雨资料欠缺流域分布式水文模拟的实际需求。  相似文献   

19.
To determine selected water pollution parameters of the Anyang River (one of the biggest contributory branches of the Han River in Korea) and its main tributaries, the geological and topographical and rainfall features in its basin were investigated, and the resulting data were tabulated. Samples were collected at the upper, mid and down parts of the Anyang River and its branches and were analyzed based on biochemical and chemical methods, Korean biotic index (KBI) and Saprobien systems. Selected parameters of concern include BOD, heavy metals, nonpoint pollution and sewage discharge. The Anyang River basin has a torrential heavy rainfall; however, the rate of rainfall significantly varies from season to season. Water pollution levels in the dry season increase dramatically. The mainstream of the Anyang River is classified as fifth grade polysaprobic water according to Saprobien system. In addition, the biotic index is over 2.5 in overall. General pollution at the junction of the Anyang River and each branch stream varies. Possible countermeasures to improve the water quality of the river include intercept the non-treated waste water and sewage at the Anyang River junction and each branch stream, enforcement of water management during the rainy season, and continuous investment on environmental restoration.  相似文献   

20.
Climate change is receiving more attention from researchers as the frequency of occurrence of severe natural disasters is getting higher. Tropical countries like Malaysia have no distinct four seasons; rainfall has become the popular parameter to assess climate change. Conventional ways that determine rainfall trends can only provide a general result in single direction for the whole study period. In this study, rainfall series were modelled using additive Holt–Winters method to examine the rainfall pattern in Langat River Basin, Malaysia. Nine homogeneous series of more than 25 years data and less than 10% missing data were selected. Goodness of fit of the forecasted models was measured. It was found that seasonal rainfall model forecasts are generally better than the monthly rainfall model forecasts. Three stations in the western region exhibited increasing trend. Rainfall in southern region showed fluctuation. Increasing trends were discovered at stations in the south-eastern region except the seasonal analysis at station 45253. Decreasing trend was found at station 2818110 in the east, while increasing trend was shown at station 44320 that represents the north-eastern region. The accuracies of both rainfall model forecasts were tested using the recorded data of years 2010–2012. Most of the forecasts are acceptable.  相似文献   

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