A Number Description of Ghanaian Water Quality—A Case Study of the Southwestern and Coastal Rivers Systems of Ghana

Abstract

The CSIR Water Research Institute undertook water quality monitoring and assessment of the Southwestern and the Coastal Rivers Systems of Ghana from 2005 to 2008 for the Water Resources Commission of Ghana (WRC) under WRIS II Project, a Danish Government Funded Project. The Southwestern and the Coastal Rivers Systems cover approximately 30% of the total drainage basins of Ghana. A total of 19 surface water stations were selected for the monitoring programme. The Adapted Water Quality Index (WQI) was to be used as a tool to classify the overall ambient water quality at the 19 different stations. The index classified water quality into one of four categories: good (Class I, >80), fairly good (Class II, 50 -80), poor (Class III, 25 -50), and grossly polluted (Class IV, <25). This paper presents the Water Quality Index approach to the assessment of water quality of the waters in the different stations during the period of study. These ten water quality parameters were used to determine the water quality index (WQI): Dissolved Oxygen (DO % Saturation), Biochemical Oxygen Demand (BOD), Ammonium Nitrogen (NH 4 -N), Faecal Coliform (FC), pH, Nitrate as Nitrogen (NO 3 -N), Phosphate as Phosphorus (PO 4 -P), Total Suspended Solids (TSS), Conductivity and Temperature. Evaluation of the waters with the WQI indicated that most Ghanaian waters are currently in Class II, the fairly good water quality state, but with variations in this range within the seasons and stations, and from one water body to the other. Potroase in the Densu basin had the best water quality during the study period while Nsawam had the poorest. Efforts should be made to prevent further pollution of the waters to improve their quality.

Assessment of surface water quality status of the Aby Lagoon System in the Western Region of Ghana

“…The index gives a single value that represents the overall suitability of water quality for a specific intended purpose such as drinking, irrigation or aquatic life protection. Several indices such as the Solway Index and River Ganga Index among several others have been successfully developed and applied for the assessment of water quality ( Darko et al., 2013 ; Gibrilla et al., 2011 ; Tirkey et al., 2013 ; Zeid et al., 2017 ). However, the WQI developed by the Canadian Council for Ministers of the Environment (CCME WQI) has increasingly become the most commonly used because it is not only relatively more robust but also flexible in adapting to various water quality parameters and guidelines ( CCME, 2001 ).…”

Relative water quality index (ReWQI) – a new method for aggregate water quality assessment

“…(2) WQI is established with the weight of each surveyed parameter: the United States (Ott, 1978a;1978b; US EPA NOAA 2012); South Africa (Cooper et al, 2000); Taiwan (Liou et al, 2004); Turkey (Boyacioglu, 2007); Malaysia (Abdullah et al, 2008); India (Mishra et al, 2008); Thailand (Prakirake et al, 2009); Ghana (Darko et al 2013). These indices have different formulations, but all are based on calculating sums, or taking the arithmetic mean, geometric mean of individual indices (subindices) according to the method proposed by Ott, 1978b that standardizes by segmental linear function to build the schema for each individual index.…”

“…Currently, a number of countries around the world including Vietnam are adopting the method of aggregated assessment of water quality under the three following main methods: Water Quality Index (WQI) is established without a weighting factor of each surveyed parameter: Oregon (USA) (Cude, 2001); Canada (CCME, 2001); New Zealand (Nagels et al , 2001); Vietnam (Pham et al , 2011; VEA, 2011); India (Pati et al , 2012). The Indices WQI are calculated easily, but they have the fundamental limitation that cannot be used to compare water quality at different observation points because the weight of each surveyed parameter is not taken into account. WQI is established with the weight of each surveyed parameter: the United States (Ott, 1978a; 1978b; US EPA NOAA 2012); South Africa (Cooper et al , 2000); Taiwan (Liou et al , 2004); Turkey (Boyacioglu, 2007); Malaysia (Abdullah et al , 2008); India (Mishra et al , 2008); Thailand (Prakirake et al , 2009); Ghana (Darko et al 2013). These indices have different formulations, but all are based on calculating sums, or taking the arithmetic mean, geometric mean of individual indices (subindices) according to the method proposed by Ott, 1978b that standardizes by segmental linear function to build the schema for each individual index.…”

“…WQI is established with the weight of each surveyed parameter: the United States (Ott, 1978a; 1978b; US EPA NOAA 2012); South Africa (Cooper et al , 2000); Taiwan (Liou et al , 2004); Turkey (Boyacioglu, 2007); Malaysia (Abdullah et al , 2008); India (Mishra et al , 2008); Thailand (Prakirake et al , 2009); Ghana (Darko et al 2013).…”

Assessing Coastal Water Quality through an Overall Index

“…In 2012, the U.S. Environmental Protection Agency assessed coastal water quality by applying an index based on percentage of water quality parameters that were in good or poor condition [21]. Darko et al (2013) used the Solway form to calculate WQI for coastal waters in Ghana [22]. Nguyen et al -It can be seen that studies on WQI have focused more on surface water [2] and groundwater than on coastal and sea waters.…”