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Department of Geography


Effect of climate and land-use change on river hydrology of Thailand, revealed using statistical analysis of meteorological and river-discharge time-series data


Water resources will be a key issue this century in SE Asia, and Thailand is no
exception. Changes in the water balance may be climatically driven but, in
Thailand, rapid land use change within the last 40 years may be responsible for
inducing change or masking climatic signals. Within the LINK project new
statistical methods are being developed to study and forecast trends in rainfall
and runoff. The software will be transferred to the RID to aid in water
resources prediction and planning.

In Thailand there have been historical reports of severe floods and droughts.
About 21 years of mild drought, 35 years of drought and 4 years of severe
drought were reported between 1831 and 1999. In the last 20 years droughts
occurred in 1978, 1986, 1987, 1990, 1993, 1999. The 1993 drought extended to
every region and caused water shortage for agriculture, industrial and domestic
consumption. Besides drought, more frequent flooding have been faced by those
living and farming in Thailand especially in the lower part of the Chao Phraya
basin. The LINK project is using data-based mechanistic (DBM) modelling of
time-series of 20 years of rainfall and discharge data for a number of key
catchments. The aim is to objectively identify annual cycle, extreme events, and
to forecast future rainfall and discharge.

Older records and the influence of land use change are also being considered.
Rapid land use change, which has occurred within the last 40 years, can be
quantified directly using historical air photographs and remote sensing methods.
An indirect method is to analysis changes in the suspended sediment loads of
rivers within catchments that were previously dominated by virgin forest.
Periods, or trends, in forest removal and agricultural activity may be isolated
through time series analysis of the sediment data. Within the Mae Chaem
catchment of NW Thailand, sedimentological studies of ancient river sediment
deposits, coupled with flood level modelling, are being used to extend the flood
record back in beyond the date of the first gauge record in 1954.

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