Restoration of historical hydrological data of Tonle Sap Lake and its surrounding areas

Tonle Sap Lake (TSL) is the largest freshwater lake on the Indochina Peninsula. It was only recently that hydrological data needed for understanding the hydrological characteristics of TSL and surrounding areas became available. In this study, historical hydrologic data from 1982 to 2004 at main observation stations at and near TSL (Phnom Penh Port, Prek Kdam and Kompong Luong) were restored by the continuous observed water data at Kompong Cham and time-series changes of TSL and its surrounding areas were analysed. The following approaches were taken in this study: (1) A method for estimating following main water budget items for TSL and surrounding areas was developed. This estimation method, based on routinely available hydrologic data only in TSL area, was constructed. (i) The volume of TSL (ii) The discharge of the Tonle Sap River (iii) The inflow from the floodplain to TSL (2) Past hydrological data for more than 20 years was reconstructed with multiple correlation analysis. Then, the three water budget terms listed above were estimated in the interested period by inputting this reconstructed hydrological data into each estimation method developed in (1). The method developed in (1) was verified on the basis of recent data that include relatively large amount of data. The past hydrological data estimated in (2) were compared with the limited past observed data and showed good agreement. According to the estimation results, the storage volume of TSL did not change significantly during the period of interest. The values of the discharge of the Tonle Sap River did not seem to change substantially, either, in terms of annual maximum discharge or annual total discharge. In contrast, the inflow from the floodplain was found to have increased slightly in recent years than in previous years. Copyright © 2008 John Wiley & Sons, Ltd.