Development and Application of a Distributed Conceptual Hydrological Model to Simulate Runoff in the Be River Basin and the Water Transfer Capacity to the Saigon River Basin,Vietnam

A distributed conceptual model(FRASC(Flow Routed Accumulation Simulation in a Catchment))has been developed,in which a rainfall-runoff module is modified from an original lumped conceptual model(Xinanjiang)via a GIS(Geographic Information System)-aided approach and a water allocation module contains reservoirs,water users and hydropower plants.The model is relatively easy to use and can easily obtain input data,but still has the ability to generate hydrological information at many points within a catchment.The model application to the Be River basin is evaluated and shows to be reliable in terms of close agreements between simulated and observed series.Daily natural flow rates for 36 years are simulated at 7,981 grid cells within a studied area of 7,650 km^2.Based on this simulated database,design discharges are predicted in various probabilities.Finally,the research determines that the water transfer capacity from the Be River basin to the Saigon River basin reaches 14%,18% and 23% of a planned value of 75 m^3/s during the dry period in a wet year(P10%),average year(P50%)and dry year(P90%),respectively.

Assessing and Forecasting Saline Intrusion in theVietnamese Mekong Delta Under the Impact of Upstreamflow and Sea Level Rise

Saline intrusion is a hot issue and has always been of concern in the VMD(Vietnamese Mekong Delta),especially in the context of many changes of impact factors such as upstream flows and SLR(Sea Levels Rise).Vulnerability to changes in the upstream flows and SLR ismust-have reasons for updated and interpreted information.This information is used for exploiting of soil and water resources.MIKE 11 model was successfully applied to assess the saline intrusion.The study provided the picture of the saline intrusion in the dry season from January to May in the VMD in the existing situation(2015 and 2016)and the future(2030 and 2050)under the impact of flow at Kratie in various frequencies of 18%,50%and 85%based on the time series of 2001-2016,and SLR according to RCP(Representative Concentration Pathway)4.5 scenario of MONRE(Ministry of Natural Resources and Environment)of Vietnam issued in 2016.The results show that in the year 2015 the ASI(Saline Intrusion Area)in the VMD was relatively low due to moderate tidal level and high Kratie discharge(P=18%).The scenario like the situation in 2016 and in the future ASI increased significantly compared to the 2015 baseline scenario which shows that the VMD is very vulnerable to saline intrusion.Based on multivariate regression analysis,the study also presented the formulas for the relationship between the ASI of 0.25 g/L,2.5 g/L and 4.0 g/L thresholds and the impact factors such as the average discharge at Kratie and the maximum daily tidal level in East Coast during the dry season from January to May.With an adjusted R2 at 0.913-0.974,these formulas are believed to be reliable for predicting ASIs based on the Kratie flow and the East Coast tidal level.