*2.1.1 Location, climate and drainage*

The Ahafo-Ano South District (**Figure 1**), is located between longitude 1°45′ and 2°20'W and latitude 6°42′ and 7°10'N with an area of about 1190.7km2 and an estimated population as at 2010 census to be approximately 121, 659. The district is bordered to the north-east by Tano-North District, north-west by Ahafo-Ano North District; south by Atwima Nwabiagya district and to the east by Offinso-North Municipal Topography is generally undulating with dominant hills being Aya, Kwamisa and Tinte hills, which run from the west towards the northeast. The highest elevation is about 763 meters above mean sea level [11]. According to [12], the area falls within the wet semi-equatorial climatic region of Ghana, which is characterized by the occurrence of two rainy seasons. The major season occurs normally between March and June while the minor season spans September to November. The average annual precipitation is about 1,700 mm - 1850 mm per year while the mean annual temperature is around 30°C with the lowest temperature being about 26.1°C. Relative humidity range is 70–75%. The area lies within the semi-deciduous forest belt with

**Figure 1.** *Geology map of the study area.*

vegetation types controlled by precipitation and groundwater. Prominent rivers draining the area include Mankran, Abu and Aboabo rivers and their tributaries.

## *2.1.2 Geology, soil and natural resources*

The area is underlain by the paleo-proterozoic Birimian metasediments subgroup. Common rock include phyllites and schist-intruded with their syngenetic basin-type granitoids [13]. The area lies within the Kumasi-Offin-Dwinyama-Bechemso belt [14], which contains extensive mineral deposits of great commercial significance such as gold, bauxite, manganese deposits as well as extensive granitic outcrop within which commercial quarrying operations occur. Gold-bearing rocks are very widespread and are commonly found and mined communities including Afrensini, Piniwutrim, Amakrom, Aburaso, Ahwirewam, Nyamebekyire, Kunsu, Mankranso, Sabronum, Barniekrom and many other parts of the District. The district is one the most important when it comes to natural resources in Ghana. It large forest reserves, namely, Tinte, Tano, Opuro River, Kwamisa forest reserves, parts of Asufufu Basin and Offin-North forest reserves. The study area is a major food basket in Ghana. About 80% of the land is arable, over 60% of which is used for agriculture. The cultivation of cash crops such as cocoa and cashew is very extensive with food crops such as corn, rice, bananas, cassava, as well as vegetables such as tomatoes, cabbage, lettuce. As briefly highlighted elsewhere, the district is known for extensive illegal artisanal gold mining operations due to the widespread gold deposits. Bauxite deposits are found at Aya Hills and Mpasaaso while manganese deposits can be found at Asirebuo Camp, close to the south of Mpasaaso. There are also clay deposits at Hwibaa, Wioso, Asuadei, Biemso II and Mankranso which have been tested by the Building and Road Research Institute (BRRI) as one of the richest clay deposits in the country [11].

The distribution of soils in the area is as shown in **Figure 2**. Three different soil types are commonly found in the area, namely Ferric Acrisols Rhodic Nitosols and

**Figure 2.** *Soil map of the study area.*

*Effects of Illegal Artisanal Gold Mining Operations on Groundwater Quality in Ghana… DOI: http://dx.doi.org/10.5772/intechopen.100242*

Haplic Alisols [15] (**Figure 2**). Ferric acrisols are the dominant soil in the district follow by nitosols and then alisols. Ferric acrisols is a clay-rich soil and is associated with humid, tropical climates and it mostly supports forest areas. Limited cultivation occurs in areas underlain by acrisols due to their low fertility and the toxic amount of aluminum. Nitosols is a deep, red, well-drained soil with a clay content of more than 40% and dominantly from moderate to strong well-develop fine to mouth angular blocky structure [16].
