A novel method of sensitivity analysis testing by applying the DRASTIC and fuzzy optimization methods to assess groundwater vulnerability to pollution: the case of the Senegal River basin in Mali

Abstract. Vulnerability to groundwater pollution in the Senegal River basin was studied by two different but complementary methods: the DRASTIC method (which evaluates the intrinsic vulnerability) and the fuzzy method (which assesses the specific vulnerability by taking into account the continuity of the parameters). The validation of this application has been tested by comparing the connection in groundwater and distribution of different established classes of vulnerabilities as well as the nitrate distribution in the study area. Three vulnerability classes (low, medium and high) have been identified by both the DRASTIC method and the fuzzy method (between which the normalized model was used). An integrated analysis reveals that high classes with 14.64 % (for the DRASTIC method), 21.68 % (for the normalized DRASTIC method) and 18.92 % (for the fuzzy method) are not the most dominant. In addition, a new method for sensitivity analysis was used to identify (and confirm) the main parameters which impact the vulnerability to pollution with fuzzy membership. The results showed that the vadose zone is the main parameter which impacts groundwater vulnerability to pollution while net recharge contributes least to pollution in the study area. It was also found that the fuzzy method better assesses the vulnerability to pollution with a coincidence rate of 81.13 % versus that of 77.35 % for the DRASTIC method. These results serve as a guide for policymakers to identify areas sensitive to pollution before such sites are used for socioeconomic infrastructures.

Download Full-text

A novel method of sensitivity analysis testing by applying drastic method and fuzzy optimization method to assess Groundwater vulnerability to pollution, case of Senegal River basin in Mali

10.5194/nhess-2017-116 ◽

2017 ◽

Author(s):

Keita Souleymane ◽

Tang Zhonghua

Keyword(s):

Sensitivity Analysis ◽

Fuzzy Optimization ◽

Groundwater Vulnerability ◽

Optimization Method ◽

Integrated Analysis ◽

Fuzzy Method ◽

Senegal River ◽

Drastic Method ◽

Senegal River Basin ◽

Nitrate Distribution

Abstract. Vulnerability to groundwater pollution from Senegal basin was studied by two different but complementary methods: the DRASTIC method (which evaluates the intrinsic vulnerability) and the fuzzy method (which assesses the specific vulnerability taking into account continuity of the parameters). The validation of this application has been tested by comparing the membership in groundwater and distribution of different classes of vulnerabilities established as well as the nitrate distribution in the study area. Three vulnerability classes (low, medium and high) have been identified by both the DRASTIC method and by fuzzy method (passing by normalized model). An integrated analysis reveals that high class with 14.64 % (for the DRASTIC method), 21.68 % (for normalized DRASTIC method) and the very high grade 18.92 % (for that of fuzzy) are not the most dominant. In addition, a new method for sensitivity analysis was used to identify (and confirm) the main parameters which impact de vulnerability to pollution with fuzzy membership. And the results showed that vadose is the main parameter which impacts groundwater vulnerability to pollution while net recharge has the least contribution to pollution in the study area. It was found also that Fuzzy method better assesses the vulnerability to pollution with a coincidence rate of 81.13 % against 77.35 % for the DRASTIC method. These results are a guide for policy makers on protection areas sensitive to pollution and identification of the sites before later hosting the socio-economic infrastructures.

Download Full-text

Trend and Sensitivity Analysis of Reference Evapotranspiration in the Senegal River Basin Using NASA Meteorological Data

Water ◽

10.3390/w12071957 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1957

Author(s):

Papa Malick Ndiaye ◽

Ansoumana Bodian ◽

Lamine Diop ◽

Abdoulaye Deme ◽

Alain Dezetter ◽

...

Keyword(s):

Sensitivity Analysis ◽

Wind Speed ◽

Relative Humidity ◽

River Basin ◽

Reference Evapotranspiration ◽

Climatic Variables ◽

Maximum Temperature ◽

Senegal River ◽

Senegal River Basin ◽

Basin Area

Understanding evapotranspiration and its long-term trends is essential for water cycle studies, modeling and for water uses. Spatial and temporal analysis of evapotranspiration is therefore important for the management of water resources, particularly in the context of climate change. The objective of this study is to analyze the trend of reference evapotranspiration (ET0) as well as its sensitivity to climatic variables in the Senegal River basin. Mann-Kendall’s test and Sen’s slope were used to detect trends and amplitude changes in ET0 and climatic variables that most influence ET0. Results show a significant increase in annual ET0 for 32% of the watershed area over the 1984–2017 period. A significant decrease in annual ET0 is observed for less than 1% of the basin area, mainly in the Sahelian zone. On a seasonal scale, ET0 increases significantly for 32% of the basin area during the dry season and decreases significantly for 4% of the basin during the rainy season. Annual maximum, minimum temperatures and relative humidity increase significantly for 68%, 81% and 37% of the basin, respectively. However, a significant decrease in wind speed is noted in the Sahelian part of the basin. The wind speed decrease and relative humidity increase lead to the decrease in ET0 and highlight a “paradox of evaporation” in the Sahelian part of the Senegal River basin. Sensitivity analysis reveals that, in the Senegal River basin, ET0 is more sensitive to relative humidity, maximum temperature and solar radiation.

Download Full-text