GIS-aided spatial and temporal mapping of reservoir water quality in an agricultural watershed : a case study of Mae Thang Reservoir, Northern Thailand | |
| Author | Warinya Thothong |
| Call Number | AIT Thesis no.NR-05-04 |
| Subject(s) | Water quality--Thailand, Northern Geographic information systems--Thailand, Northern |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. NR-05-04 |
| Abstract | Since water reservoirs are often located at the outlet of catchments, inappropriate landuse practices upstream may generate several problems in the reservoir especially water quality degradation. In order to better understand the dynamic changes of water quality in the Mae Thang reservoir of Thailand, built up for irrigation and fish production purposes, monitoring the parameters (i.e. temperature, turbidity, electrical conductivity, dissolved oxygen, chlorophyll-a, hydrogen sulfide and methane) related to water quality was carried out at the beginning of rainy season (May), during the rainy season (July and September) and during the dry season (December) of 2004. In-situ measurement was done by using a multi-parameter probe together with general chemical and biological study. The data was analyzed and displayed by the integration of GIS technique. At the beginning of rainy season, a stable thermal stratification was observed, with contrasted differences between the epilimnion (in contact with atmosphere) with high dissolved oxygen and chlorophyll-a contents and the hypolimnion (isolated from atmosphere) with low dissolved oxygen concentration (c.a. 2 mg/I near the bottom). Reducing conditions are fulfilled for sulfate reduction to toxic gas as hydrogen sulfide production (c.a. 3 mg/l at hypolimnion). During the rainy season, dissolved oxygen levels in the hypolimnion were thoroughly increased (7.33 mg/l and 8.66 mg/l in July and September respectively) with much higher suspended sediment load (up to c.a. 1600 mg/l near lake bottom) due to new water inflow from the watershed. Chlorophyll-a concentration increased due to nutrient supply in the water column. Reducing condition had switched to oxidizing condition, therefore low hydrogen sulfide was observed in the water column. Electrical conductivity was low in hypolimnion due to the dilution capacity of new water inflow from the watershed. During the dry season, the mineralization of organic matter consumed large amount of dissolved oxygen lead to severe dissolved oxygen depletion (c.a. 1 mg/l near the bottom). Temperature showed positive relationship with chlorophyll-a due to higher temperature, lead to the increasing the rate of biological productivity in epilimnion. Electrical conductivity showed highly negative relationship with turbidity in hypolimnion zone which reflect the influence of new water inflow in the reservoir. During the study period, the concentrations of suspended matters, dissolved oxygen and hydrogen sulfide were exceeded the threshold values for water quality standard for irrigation and fishery in Thailand, and therefore may cause the negative impacts on irrigated areas and aquatic organisms in the reservoir. However, monitoring of water quality in the Mae Thang reservoir should be done several years in order to better understand the pattern of water quality dynamics in the reservoir. |
| Year | 2005 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. NR-05-04 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Development and Sustainability (DDS) |
| Academic Program/FoS | Natural Resources Management (NRM) |
| Chairperson(s) | Shrestha, Rajendra Prasad; |
| Examination Committee(s) | Clemente, Roberto S. ;Yi, Yang ; |
| Scholarship Donor(s) | Her Majesty the Queen of Thailand; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2005 |