Monthly flow forecasting of the Ganges River with PAR model

Forecasting of the Ganges flow with sufficient accuracy and adequate lead-time can favorably impact the socio-economic development of Bangladesh. This is especially true in view of the shifting government policy to the development of surface water in preference to groundwater due to reported arsenic problems in groundwater and progression of saline water intrusion from the Bay of Bengal in the dry season. A significant development of surface water is envisioned through possible construction of a barrage on the Ganges river within Bangladesh for diversion of its water to the south-west, south-central and north-west hydrological regions of the country. Due to natural and man-made variability in climate, land use and socio-economic conditions, a high degree of uncertainty is inherent with the amount of water to be available over the planning period of the barrage. So, it is necessary to develop a suitable mathematical model that can be used for forecasting as well as generation of synthetic flow sequences and which can capture the uncertainties. This can be accomplished through the development of time series models such as Box-Jenkins Seasonal Autoregressive Integrated Moving Average model and structural models (deseasonalized and periodic). The stochastic behavior of the possible barrage in meeting the water requirements of the above regions can then be simulated and subsequently risk-related performance can be evaluated in terms of reliability, resiliency and vulnerability in overall water management. In this paper, a Periodic Autoregressive model is developed for forecasting the monthly flow of the Ganges at Farakka. The results indicate that the model can be used for monthly forecasting and generation of the Ganges flow, which may have some practical value for water resources and agricultural management in Bangladesh.