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INDICATORS OF CLIMATE CHANGE ACROSS THE SOUTHCENTRAL REGION Tran Hong Thai1, Hoang Anh Huy2, Nguyen Dang Mau3, Hoang Van Dai3 1Vietnam Meteorological and Hydrological Administration 2HaNoi University of Natural Resources and Environment 3Vietnam Institute of Meteorology, Hydrology and Climate change ABSTRACT: In this study, we focus on the findings of the indicators of climate change across the SouthCentral region based on assessing the trends of temperature (mean, maximum and minimum) and rainfall as well as drought conditions. The change trends of climatic variables are tested by the simple linear method at significance level of 0.05 (corresponding to the 95% confidence level). The observation data is updated up to 2017. The results show that the annual mean temperature tends to increase at 15 stations, where, the increase in temperature in the dry season is greater than that in rainy season. The increases in annual temperature are mostly from 0.01 to 0.03 per year and accepted by the 90% confidence level. The increase trends of annual rainfall are mostly from 0.1 to 1.35% per year. The A index is mostly found by increase trend that the wet condition is found at most station. In addition, the increase trend of the drought condition defined by the decrease trend of the A index at some southern stations in the SouthCentral region. However, the trends of both rainfall and A index are not mostly at significance level of 0.05. Keywords: Indicators of climate change, Rainfall, temperature, South-Central region. |
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STUDY OF DROUGHTS IN CA MAU PROVINCE: CHARACTERISTICS AND PREDICTION CAPABILITIES Nguyen Van Thang1, Mai Van Khiem1, Tran Dinh Trong1 1Viet Nam Institute of Meteorology, Hydrology and Climate change ABSTRACT: This paper studies the characteristics of droughts in Ca Mau and its prediction capabilities. It shows that drought cycle in Ca Mau annually occurs with dry season. The most severe droughts occur in January, February and March with the frequency of 90 – 95%. Average duration of drought season is about 4 months which can be longer in few years. Longer duration drought and more severe intensity drought mostly occur in the El-Nino year. In addition, by applying the Regional Spectral Model (RSM) for drought prediction, the results show that the RSM model captures well the inter-annual variation of the SPI index at timescale of 12 months, especially during severe water scarcity periods. Underestimated errors in the predicted SPI value can be bias-corrected for more proper determination of droughts from the RSM output. An important issue of drought prediction is warning of drought intensity during either dry or rainy season. The assessment of long-term water scarcity using the SPI index can provide warning of drought intensity in future. Keywords: Drought, Duration, Intensity, The RSM model, The SPI index. |
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A STUDY ON DROUGHT IN THE SOUTH-CENTRAL REGION: DETECTION FROM THE OBSERVATION AND THE BIAS-CORRECTION RAINFALL PROJECTIONS OF NATIONAL CLIMATE CHANGE SCENARIOS Mai Kim Lien1, Tran Duy Hien2 1Department of Climate Change, MONRE 2Science and Technology, MONRE ABSTRACT: This article presents the results of detecting the trend of drought conditions in the South-Central region based on the past observation and bias-correction rainfall projections. The past observation of daily rainfall is updated up to 2017 and collected from Vietnam Meteorological and Hydrological Administration. The bias-correction daily rainfall projections are collected from Vietnam Institute of Meteorology, Hydrology and Climate change (IMHEN) during the periods of 1986 - 2005, 2016 - 2035, 2036 - 2065 and 2080 - 2099 according to both RCP4.5 and RCP8.5 scenarios. The Standardized Precipitation Index (SPI) and minimum value of SPI (SPI_min) are used to define the mean drought condition and the most extreme drought condition. The past trend of drought conditions is found that the decreasing trends of mean drought condition and increasing trends of the severity level. The future trend of drought conditions according to both RCP4.5 and RCP8.5 is found that it is similar to the past trend. Where, the mean drought condition is generally found by slight decreasing trends. However, the most extreme of drought condition is significantly found by increasing trends of drought at shorter timescales (1- and 3-month time scales). Keywords: Drought condition, extreme drought, SPI, SPI_min, South-Central region. |
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AN INVESTIGATION OF RAINFALL DEFICIENCY IN OCTOBER AND NOVEMBER IN THE CENTRAL VIETNAM DURING THE 1997 - 1998 EL NINO EVENT Nguyen Van Thang1, Vu Van Thang1 1Viet Nam Institute of Meteorology, Hydrology and Climate change ABSTRACT: In this article, the rainfall deficiency in October, November over the Central Vietnam during the 1997 - 1998 El Nino event are investigated based on large-scale moisture transport circulation, wind at 10m and 850hPa levels and sea-level pressure.The results show that there were 9 months in total of 12 months from May1997 to April1998 of this El Nino event observed the rainfall deficiency over some climatic regions of Viet Nam. In which, the most significant deficiency occurred in October, November 1997 in the Central Vietnam in a range of 100 - 150 mm, especially the deficiency reached up to 200 mm at some heavy rainfall centers such as Ky Anh, Hue, Tam Ky, Tra My, Ba To. This deficiency seems to be caused by a weakening of the North East monsoon circulation in comparison to the long-term mean, which leads to formation of an anomalous anticyclonic vortex over the East Sea. The appearance of anticyclonic vortex causes a decrease in moisture transport that suppling to rainfall in the Central Viet Nam. In addition, there is only a main source of moisture from East Sea that favors rainfall formation over Central Viet Nam is lower than climatology. Keywords: El Nino, Moisture transport, Rainfall deficit |
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INTEGRATION OF SWAT AND MODFLOW MODEL TO ASSESS THE SURFACE AND GROUNDWATER AVAILABILITY: A CASE STUDY OF DONG NAI BASIN IN 2015 – 2016 Do Xuan Khanh1, Nguyen Bach Thao2 1 Thuyloi University 2 Hanoi University of Mining and Geology ABSTRACT: Water is one of the most essential natural resources . A good assessment of both surface and groundwater always leads to an effective and sustainable water resources management. In Vietnam, the management of water resources has mainly focused on surface water, however, the problems related to groundwater have not been managed properly. This study aims to assess surface and groundwater availability in Dong Nai river basin by integrating SWAT and MODFLOW models. These models run individually and integrated through the recharge rates. The simulation results were then compared and showed good agreement with observed data. The results showed Tuyen Lam, Da Huoai and Dak Song districts are the locations which have high surface water availability, in the range of 40 50 l/s/km2. The groundwater simulation indicated the areas having high groundwater availability are located at the same places with the regions having high surface water. Dak Song is the region having the highest groundwater availability with around 9 l/s/km2. Keywords: Surface water, groundwater, SWAT, MODFLOW, Dong Nai, recharge rates. |
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STUDY ON A CASE STUDY OF ABNORMAL HEAT WAVES IN THE WINTER IN THE NORTHERN AREAS OF VIET NAM IN 2010 AND 2015 Vo Van Hoa1, Vu Anh Tuan2, Du Duc Tien2, Mai Khanh Hung2, Luong Thi Thanh Huyen2, Luu Khanh Huyen2 1Red-river Delta Regional Hydro-Meteorological Center 2National Center for Hydro-Meteorological Forecasting ABSTRACT: Under the condition of climate change, the abnormal extreme weather phenomena has been increasing in both of frequency and intensity, especially the abnormal heat waves in the winter. The paper shows the results of thermodynamic analysis that caused two abnormal heat waves in the winter in northern areas of Viet Nam (one case occurred in the early winter, the other occurred at the end of winter). Based on the largescale synoptic pattern analysis, we found that the key reason that caused abnormal heat waves in the winter in northern areas of Viet Nam is due to the unusual activities of western hot low pressure and western Pacific subtropical high pressure in combination with “foehn” effect caused by Hoang Lien Son high rock mountain . In some cases, the combination between strong cold surge that descending from the south China and western hot low pressure also caused an abnormal heat wave in the winter. Keywords: Abnormal heat wave, western hot low pressure, foehn effect. |
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ARTIFICAL NEURON NETWORK FOR FLOOD FORECASTING AS INFLOW OF PLEIKRONG RESERVOIR IN POKO RIVER Truong Van Anh1, Duong Tien Dat1 1Department of Hydrology and Meteorology, Hanoi University of Natural Resources and Environment ABSTRACT: In Vietnam, modern and small hydropower reservoirs play an important role in socio-economic development. However, the effective operation of such reservoirs based on the argument of the release function and expected future inflow is one of the most important variables that the operators will reply on to control such release. In other words, to attenuate floods, the operators have to release water in advance, so to create an empty volume (flood volume) in the reservoir, into which the excess in flow can be accommodated during the flood events. Therefore, the predicted periods should be as long as possible to create a sufficient large flood volume in the reservoir, while releasing a flow that is not so high to mitigate the impacts on downstream. Nevertheless, predicting the future inflow is still a big challenge for the local hydrologists due to the lack of information and technology. This paper proposes a method to predict the inflow of Pleikrong hydropower reservoir which located in downstream of Poko river, a second tributary of SeSan River and the observation data is insufficient and incorrect. This method uses MIKE NAM to construct the inflow then the Artificial Neuron Network to predict the inflow based on the availability of data. The result is surprising when R2for 6 hourly forecasted inflow is about 0.97 and for 12 hourly forecasted is about 0.79 which correspond to the catchment concentration time of 9 hours. The results of this study will hopefully be an example to apply on many case studies in Viet Nam and other ungauged stations system. Keywords: Reservoir management, flood forecast, MIKE NAM, ANN, PleiKrong. |
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ASSESSING THE IMPACTS OF THE CHANGES IN THE UPSTREAM FLOW AND SEA LEVEL RISE DUE TO CLIMATE CHANGE ON SEAWATER INTRUSION IN HO CHI MINH CITY USING THE HEC - RAS 1D MODEL Nguyen Thi Diem Thuy1, Nguyen Ky Phung2, Nguyen Xuan Hoan1, Dao Nguyen Khoi3 1Ho Chi Minh City University of Food Industry, Ho Chi Minh City, Vietnam 2Institute for Computational Science and Technology, Ho Chi Minh City, Vietnam 3Faculty of Environment, VNU-HCM University of Science, Ho Chi Minh City, Vietnam ABSTRACT: The aim of this study was to assess the impacts of the changes in upstream flow and sea level rise due to climate change on seawater intrusion in the Sai Gon and Dong Nai Rivers in Ho Chi Minh City. The HEC-RAS model was used for simulating the salinity intrusion. The results of model calibration and validation indicated that the HEC-RAS model could simulate reasonably the streamflow and salinity concentration with NSE values exceeding 0.5 for both calibration and validation periods. Based on the results in the calibration in the HEC-RAS model, differences in salinity concentration under the separate and combined impacts of the changes in the upstream flow and sea level rise were analyzed. The results indicated that the salinity intrusion is likely to increase by 0.9 to 13% under the impact of sea level rise, by 1.6 to 4.3% under the impact of the changes in the upstream flow, and by 2.6 to 16.9% under the combined impacts of changes in the upstream flow and sea level rise. The research obtained in this study could be useful for local authorities in proposing solutions to reduce the impacts of seawater intrusion in Ho Chi Minh City. Keywords: HEC-RAS, Ho Chi Minh City, sea level rise, seawater intrusion, changes of river flow in the upstream. |
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RESEARCH ON BOTTOM MORPHOLOGY AND LITHODYNAMIC PROCESSES IN THE COASTAL AREA BY USING NUMERICAL MODEL: CASE STUDIES OF CAN GIO AND CUA LAP, SOUTHERN VIETNAM Nguyen Thi Bay1, Dao NguyenKhoi2, Tran Thi Kim3, Nguyen Ky Phung4 1HCMC University of Technology 2HCMC University of Science 3HCMC University of Natural Resources and Environment 4HCMC Department of Science and Technology ABSTRACT: A numerical model to simulate Litho-dynamic processes and bottom morphology at the coastal area such as the flow, sediment transport and bed changes under the effects of tides, waves and winds have been suggested. The model is based on the system of Reynolds equation coupled with sediment transport and bed load continuity equation. There are three verification cases of the model: verification of the tide-induced current, the wave-induced current and the sediment transportation., The results from the model are good in accordance with the analytical solution. The model is then applied to the coastal zone of Can Gio mangrove forest and Cua Lap estuary (South East of Vietnam). As a result, the trend of sediment accretion and erosion in these two areas are qualitatively in agreement with satellite observation and practical measurement. Keywords: The numerical model, Litho-dynamicprocesses, Sediment transportation, Eccretion and erosion. |
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