Climate and rainfall are extremely non-linear and complicated phenomena, which require numerical modelling to simulate for accurate prediction. We obtained local historical rainfall data for 12 meteorological stations in the Vietnamese Mekong Delta (VMD) for the 45-year period 1978–2022, to predict annual rainfall trends. A statistical time series predicting technique was used based on the autoregressive integrated moving average (ARIMA) model. We utilized the seasonal ARIMA process of the form (p,1,q)(P,1,Q) for our study area. The best seasonal autoregressive integrated moving average (SARIMA) models were then selected based on the autocorrelation function (ACF) and partial autocorrelation function (PACF), the minimum values of Akaike Information Criterion (AIC) and the Schwarz Bayesian Information (SBC). The seasonal autoregressive integrated moving average model with external regressors (SARIMAX) was discovered, and a series of SARIMA models of various orders were estimated and diagnosed. To evaluate model fitting, we used the Nash–Sutcliffe coefficient (Nash) and the root-mean-square error (RMSE). The study has shown that the SARIMA (1, 1, 1)(2, 1, 1)₁₁ and SARIMA (1, 1, 1)(2, 1, 1)₁₂ model were appropriate for analyzing and forecasting future rainfall patterns at particular meteorological station in the VMD. The results showed the SARIMA model is more reliable and provides more accurate projections than other commonly used statistical methods, notably interval forecasts. We found that interpretable and reliable near-term location-specific rainfall predicts can be provided by the SARIMA-based statistical predicting model.

Information on the relationship between rainfall intensity, duration and accumulation frequency or return period (IDF) is commonly utilized in the design and management of urban drainage systems. Can Tho City, located in the Vietnamese Mekong Delta, is a city which has recently invested heavily in upgrading its stormwater drainage systems in the hope of preventing reoccurring flood events. Yet, much of these works were designed based on obsolete and outdated IDF rainfall curves. This paper presents an updated IDF curve for design rainfall for Can Tho City. For each duration and designated return period, a cumulative distribution function (CDF) was developed using the Pearson III, Log-Pearson III, and Log-Normal distribution functions. In order to choose the best IDF rainfall curve for Can Tho City, the CDF rainfall curve and empirical formulas used in Vietnam and Asia (Vietnamese standard 7957:2008, Department of Hydrology, Ministry of Transportation, Talbot, Kimijima, and Bermard) were compared. The goodness of fit between the IDF relationship generated by the frequency analysis (CDF curve), and that predicted by the IDF empirical formulas was assessed using the efficiency index (EI), and the root mean squared error (RMSE). The IDF built from Vietnam’s standard TCVN 7957:2008 with new parameters (A = 9594, C = 0.5, b = 26, n = 0.96) showed the best performance, with the highest values of EI (0.84 $\le$EI$\le$ 0.93) and the lowest values of RMSE (2.5 $\le$RMSE$\le$ 3.2), when compared to the other remnants.

Nghiên cứu ảnh hưởng của các yếu tố địa chất, thủy văn đến ổn định bờ sông Cái Vừng, huyện Hồng Ngự, tỉnh Đồng Tháp

The water budget in the Vietnamese Mekong Delta (VMD) depends heavily on rainfall which play crucial roles in supporting agriculture, aquaculture, and local livelihoods. This study evaluated rainfall trends across the VMD from 1978 to 2022, revealing significant spatial and seasonal variations. While a few inland stations showed marginal increases in dry season rainfall, our findings indicate an overall decline in both wet and dry season rainfall across the region. This trend is particularly concerning for coastal areas, such as Ca Mau Province, which rely predominantly on rainfall due to limited upstream inflows; these areas recorded substantial declines in annual and wet season rainfall, with Sen’s slope values of –7.582 mm/year and –6.335 mm/year, respectively. Although the VMD is situated within the Asian monsoon region, geographical factors, including coastal and inland locations, exert a strong influence on rainfall variability patterns across the delta. The observed rainfall decline has critical implications for water resource management in the VMD, where climate variability is projected to increase. Although other factors, such as evapotranspiration and land use changes, also impact water availability, our study focuses on rainfall’s direct role. These findings highlight the necessity for adaptive water management strategies that account for declining rainfall, particularly in vulnerable coastal areas. This study provides a critical analysis of rainfall trends in the VMD to inform adaptive water resource strategies under climate variability, answering how these long-term trends affect the region’s water availability and resilience, and contributes to the broader understanding of climate change impacts, informing both regional adaptation strategies and global climate policy formulation.

Mục tiêu của nghiên cứu này là phân tích ảnh hưởng của các yếu tố địa chất thủy văn và gia tải đến ổn định bờ sông Chà Và, tỉnh Vĩnh Long. Ảnh vệ tinh tải về từ phần mềm Google Earth được sử dụng để đánh giá mức độ sạt lở bờ sông và mức độ đô thị hóa ven sông. Các số liệu sơ cấp và thứ cấp như địa hình, địa chất, thủy văn và sóng tàu được thu thập và phân tích. Hệ số an toàn được sử dụng để phân tích mức độ ổn định bờ sông. Các thông số đầu vào của mô hình được lấy từ các số liệu phân tích các yếu tố địa chất, mực nước, tải trọng sóng và tải trọng do quá trình đô thị hóa. Vận tốc dòng chảy thực đo được so sánh với vận tốc không xói của bùn cát cấu tạo bờ sông để đánh giá khả năng gây xói của vận tốc. Kết quả phân tích cho thấy xói lở và bồi tụ đang diễn ra dọc theo đoạn sông nghiên cứu. Vận tốc dòng chảy là một trong những nguyên nhân gây...