The performance of the BMWP biotic score, which is based on macroinvertebrates, in accurately classifying
23 sites on the River Ping system in northern Thailand, was assessed through comparison with physical and
chemical data. Sites were located on the main River Ping, a highly polluted tributary (Kha Canal), a relatively
unpolluted tributary (River Taeng) and an upland stream tributary system (River Klang). Data were collected
between December 1990 and September 1993. The purpose of the research was to determine whether the BMWP
score, originally developed in the U.K., could be employed successfully in Thailand and potentially also in other
subtropical and tropical developing countries. Biological monitoring techniques such as the BMWP score are
low-tech, rapid means of assessing water quality, and involve significantly lower financial costs than chemical
monitoring techniques. The BMWP score was capable of distinguishing between sites that were heavily impacted
by organic pollution and relatively unpolluted sites, and showed some potential to identify lower levels of pollution.
The overall performance was considered to be similar to that recorded in the U.K. It was noted during the study
that several of the taxa used in the BMWP score were absent in Thailand and that other taxa were present that
would potentially be useful indicators. The BMWP score was therefore modified by removing 15 taxa not present
in Thailand and adding 11 replacement taxa. Also, in the modified score, 6 sets of families were combined due to
taxonomic difficulties and 7 odonatan families were allocated lower scores. The modified procedure, named the
BMWPTHAI score, did not significantly alter the way in which sites were classified, but was easier to use. There
is strong potential for application of the BMWPTHAI score in Thailand and other developing countries, although
some further testing is first recommended