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The objectives of this research were to investigated (1) To study the quality of water resources in Lumpaya Sub-district in relation to ecological variations (2) To study the types and distribution of freshwater algae in Lumpaya Subdistrict, and (3) To study the relationship between the freshwater algae types and water quality as well as. To identify the freshwater algae types that specifically applicable to be used as indicator for measurement of water quality in Lumpaya Sub- district. This investigation was conducted using a single sampling of Lumpaya and the nearby flowing water at locations of the strand and the middle of the water body. These included Lummai, Pharon, Thaasab, and Mueang Sub-district, Yala Province, comprising of 11 sampling stations. Samples were analyzed and determined the flowing rate, pH, transparency, conductivity, dissolved oxygen, nitrate nitrogen content, ammonium nitrogen content, total nitrogen content, and total phosphorus. Such a single sampling was monthly conducted from June-November 2011. The result from this study showed that 1. Quality of Lumpaya water resource complied with the standard. Means parameters included the flowing rate was 0.300.20 meter per second, pH was 7.270.25, temperature was 27.901.67OC, transparency was 36.1412.19 centrimeter, conductivity was 63.0624.63 micro Siemens per centimeter, dissolved oxygen was 5.521.50 milligram per litre, nitrate nitrogen was 1.01.89 milligram per litre, ammonium nitrogen was 0.160.2 milligram per litre, total nitrogen was 0.980.67 milligram per litre and total phosphorus was 0.320.17 milligram per litre. Water quality was found variable with seasons (p-value 0.05) but not with different sampling stations and soil usages. Comparatively, better quality of Lumpaya water resource was found in dry season and in areas of non-usage soil. 2. Types and distribution of freshwater algae in Lumpaya and the nearby sub-districts were of 81 species in total with 48 genera and 5 divisions. They were (1) 12 species of Division Cyanophyta, (2) 34 species of Division Chlorophyta, (3) 26 species of Division Bacillariophyta, (4) 7 species of Division Euglenophyta, and (5) 2 species of Division Rhodophyta. 3. The relationship between water quality and freshwater algae indicated that there were 57 species that were in close relation with environmental factors of water. Such factors included the flow rate, pH, transparency, conductivity, dissolved oxygen, nitrate nitrogen, ammonium nitrogen, total nitrogen, and total phosphorus. It was also showed that specific freshwater algae inhabiting good surface water quality standard were Closterium didymotocum Ralfs., Closterium ehrenbergii Meneg h var. ehrenbergii., Closterium jenneri Ralfs., Closterium moniliferum (Bory) Ehrenb., Closterium venus var.Westii Krieg., Cloterium parvulum Wag. var. parvulum., Cosma- rium binum W.& G.S. West., Cosmarium nudum (W.B.Turner)., Cosmarium depressum var.inter- medium (Gutw.) Messik., Cylindrocystis gracilis I. Him., Euastrum sp., Hyalotheca sp., Micras- terias foliacea Bailey ex Ralfs var.,Netrium sp., Pandorina morum Bory., Pandorina morum Bory., Penium sp., Pleurotaenium sp., Staurastrum altemans Breb., Achnanthes sp., Cymbella affinis Kutzing., Eunotia sp.,Pinnularia abarjensis (Pantocsek) R. Ross., Pinnularia acrosphaeria Brebison., Pinnularia divergentissima (Grun.) Cleve., Batrachospermum sp.,and Nemalionopsis sp. It was therefore, believed that all of these specific freshwater algae were useful in indicating quality of freshwater.