Examination of Differences in Water Quality and Quantity by Reservoir Catchment with a Different Land-Use Type in the Republic of Mauritius

Fatema Nabybaccus, Don Lee, Yohan Lee, Jung Seo
2018 Sustainability  
Forest buffers contribute to enhancing the quality and availability of water in catchments. This study aims to examine the effects of forest buffers on water quality and quantity in three reservoir catchments in Mauritius, including Mare aux Vacoas (MAV), Mare Longue (ML), and La Ferme (LF). While MAV and ML are surrounded by forests, the forested area of LF was cleared for photovoltaic panels for electricity generation and agriculture. We used catchment simulation modeling and empirical data
more » ... nd empirical data analysis. The results showed that the concentrations of water quality parameters, such as conductivity, silica, total suspended solid (TSS), total organic carbon (TOC), NO 3 − , NO 2 − , and total reactive P in LF were higher than those in MAV and ML. Sparsely vegetated lands can lead to water quality degradation due to surface runoff. In addition, the water quantity per unit area for MAV and ML were greater than that for LF, which indicated that a high percentage of forest buffer cover also positively influences the quantity of water in catchments. Our findings suggest that forest buffers have a critical importance in hydrological cycles and also enhance water production, and thus should help develop an effective and innovative water resource management strategy in Mauritius. to an imminent water crisis. The FAO [4] forecasted that millions of people worldwide would be subjected to absolute water scarcity, while the vast remainder would be subjected to water stress. The expected water resource crisis may not only affect rain-fed and irrigated agriculture, but also exacerbate changes in water regimes and the availability of freshwater [5] . In order to address the water resource crisis, it is critical to mitigate deforestation, which undermines the environment's capacity to provide ecosystem services, and in particular, clean water [6]. In Mauritius, the total forest area, corresponding to about 25% of the total land area, has declined by 5 ha from 47,108 ha in 2013 to 47,103 ha in 2014. Also, the net carbon dioxide (CO 2 ) emissions have increased by 2.6% from 2012 to 2013 (Statistics Mauritius, 2014). Deforestation and forest degradation contribute to atmospheric greenhouse gas (GHG) emissions through both combustion and decomposition. A literature review shows that GHG emissions positively contribute to global warming and climate change. The emerging phenomenon of climate change, which is a serious environmental issue, coupled with increasing population puts Mauritius at risk on both national and global platforms. The freshwater reserves in Mauritius are particularly of concern because of increasing water demands resulting in the perpetual anthropogenic degradation of water. Residents in the central districts of Mauritius obtain their domestic water supplies from Mare aux Vacoas (MAV) reservoir, which is the largest potable water source in Mauritius. Over the past two decades, some parts of the state-forested land areas around the MAV reservoir have been cleared for the introduction of agriculture. A rough approximation using Google Earth satellite images showed that the patches of forest buffers, ranging from 40 m to 200 m in width, are present within the transition regions separating the agricultural areas from MAV. Since agricultural practices involve soil structure modifications and disturbances through tillage practices and the use of chemicals, these activities could impinge on the water quality of MAV. Although the MAV reservoir is favorable to high precipitation, high surface runoff could result in a contaminated sediment washoff, which could degrade the water quality of the MAV reservoir. One of the least noticeable impacts is the bioaccumulation of pesticides in the reservoir organisms and ecosystem. The intensive practice of inorganic farming around the reservoir area may contribute to the pollution of the environment through the leaching of nitrate to groundwater [7] . While the import of fertilizers increased by 16.0%, from 45,924 tons to 53,276 tons, and that of pesticides increased by 0.7%, from 2185 tons to 2201 tons from 2013 to 2014, the concern for further water contamination is omnipresent. Several researchers have attempted to elucidate the relationship between forest buffers and water quality in given catchments in countries such as the Philippines, Japan, and Kenya. For example, Dessie and Bredemeier [8] investigated the effect of deforestation on water quality based on physicochemical properties, and evaluated the community-based water resource management schemes in the Philippines. They found that the physical properties (as opposed to chemical properties) of the deforested regions were altered compared with those of the forested area. Also, Trancoso et al. [9] argued that conserving natural vegetation cover is critical for maintaining the ecological integrity and hydrological properties of large river catchments in the Brazilian Amazon. The land use and cover change (LUCC) in major catchments was analyzed to evaluate the current balance between the deforestation and conservation of natural areas in the region. Their results showed that in regions with critical levels of deforestation, more than 80% of the subcatchments had been affected. Furthermore, Masese et al. [10] combined the effects of land use, physicochemical indicators, and resident aquatic biota indicators to determine changes in the surface water quality in the Lake Victoria Basin, Kenya. They found that the increased intensity of agriculture and deforestation in the region influenced the magnitude and frequency of runoff events, and increased pesticide contamination, erosion, and sedimentation in streams and rivers. Singh and Mishra [11] found possible correlations between forest cover, water quality, and treatment costs by investigating how the drinking water was impacted by deforestation within catchments, which emphasized the urgent need to protect and conserve water resources, especially with the advent of climate change.
doi:10.3390/su10062080 fatcat:b6pewpkoy5edtdabdtqsswfhiy