Preliminary groundwater modelling of Mae Moh basin for lignite development

The Mae Moh basin is an intermontane basin of about 135 km 2 located 28 km east of Lampang city in Northern Thailand ( Fig. 1 ), where a large scale lignite open pit mine is developed by EGAT (The Electricity Generating Authority of Thailand). Recently, an aquifer with very high artesian pressure was found right under the open pit excavation area which need to be treated to ensure the stability of the excavation when the depth increases in the future. Fig. 1 Mae Moh Basin: Location and Extent A map of the Mae Moh basin in Northern Thailand, showing the location and extent of the basin. The map includes highways, rivers, and various labelled locations such as Changwat Lampang, Mae Moh Mine Area, and Mae Chang Reservoir. It also features a legend indicating different areas like open pit and mining units, power plants, mine grid, dumping area, water divide, reservoir, and diversion channel. The inset map shows the broader region including Thailand, Laos, Burma, and Kampuchea, with marked locations like Chiang Mai, Lampang, Mae Moh Mine, and Bangkok. https://www.w3.org/1999/xlink" xlink:href=" https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003761143/28ca18ae-7b36-43a5-a4f1-93d93af52533/content/pg280_1.tif "/> Fig. 2 Average Monthly Rainfall A bar graph compares average monthly rainfall in millimeters across different months. It features 12 vertical bars, each representing a month from January to December. The x-axis is labelled with the months, and the y-axis is labelled with rainfall measurements in millimeters, ranging from 0 to 200. The bars show significant rainfall from May to September, with the highest rainfall in July, followed by August and June. Rainfall is minimal from January to April and from October to December. The scheme consists of a single for all bars. https://www.w3.org/1999/xlink" xlink:href=" https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003761143/28ca18ae-7b36-43a5-a4f1-93d93af52533/content/pg281_1.tif "/> This study is a first attempt to model the relatively small but complicated aquifer system which occurs in the basin. The groundwater flow system in Mae Moh Basin Area is conceptualized as a leaky and fractured multiaquifer system with some typical hydrogeological characteristics of a small localized basin; namely, upward hydraulic gradients, the presence of a weathered limestone layer at the top of basement with high permeability, fractured zones associated with basement faults and along the basin margins could be significant location of groundwater flow etc. In the study, several possible models of steady analysis are presented to explain some observed evidences so far (up to Fall, 1991). It seems that the quasi-3D model is suitably applicable to hydrogeological characterization of Mae Moh Basin.