Groundwater recharge in Myanmar - Estimations in the Chindwin catchment by base flow separation and SWAT

Abstract

First estimations for the groundwater recharge in the Chindwin basin in Myanmar are presented in this report. This estimations are based on base flow separation and a SWAT model. Multiple base flow separation methods are applied and these are compared with the base flow produced by the SWAT model. This first estimations show a range of 248-670 mm average groundwater recharge per year, which is roughly 11-30% of the average annual rain in the catchment. The upper limit, produced by SWAT, seems to be too high, as the total flow is overestimated due to a rate of evaporation which is too low compared with remote sensing based evaporation. In the Chindwin it appeared that it is rather difficult to separate the base flow due to the highly sensitive alpha parameter, which determines the response behaviour of the base flow, also there seem to be multiple groundwater components. This makes it hard to perform base flow separation, but also increases the difficulty of calibrating the SWAT model, especially the base flow component. However the SWAT model shows a clear spatial groundwater recharge pattern even though it needs further optimization. Optimizing a (hydraulic) model can be cumbersome and especially in a developing environment as Myanmar it is also interesting to look at other possibilities/models, like Water Accounting +, which are more flexible to adapt to changes as new dams or increase in groundwater irrigation.