Potential Impact Assessment of Agricultural Practices on Water Quality in Nyanza District; A Case Study of Bishya Wetland
Abstract
A challenge of linking agricultural sector with water quality in order to combat water pollution remains worrying for the Government of Rwanda. The general objective of the study was to assess the potential impacts of agricultural practices on water quality in NYANZA District. Specifically, the study assessed agricultural practices in Bishya wetland, analyzed the level of water pollution in Bishya wetland, and demonstrated the correlation between agricultural practices and water quality from Bishya wetland. Data were obtained through questionnaires, observation, and laboratory analysis of water samples taken twice per month in six sampling points of bishya dam situated in bishya wetland starting from 4th March 2019 up to 20th August 2019. The Linear Regression Model using SPSS statistics with 95% confidence interval was used to demonstrate the correlation between agricultural inputs and water quality data for all selected physico-chemical parameters. Findings revealed that agricultural practices in Bishya wetland and surrounding areas are characterized by the presence of different crops, ineffective anti-erosions, absence of wetland margins, ineffective drainage of wetland, use of organic manures and chemical fertilizers, as well as the presence of different types of rocks and soils. Findings revealed also that all parameters have not manifested pollution, but some of them did according to Rwanda Standard Board guidelines. In sampling point1, the parameters that presented pollution were nitrites (r=0.047), phosphates(r=0.384), iron (r=0.11), and manganese(r=0.018); in sampling point2, were nitrites(r =0.010), iron (r=0.059), and chemical oxygen demand(r=0.012); in sampling point 3, were pH (r=0.048), nitrites(r =0.086), and phosphates (r=0.329); in sampling point 4, were nitrites (r =0.123), iron(r=0.182), and manganese (r=0.051); in sampling point 5,were turbidity (r=0.080), nitrites (r=0.095), phosphates(r=0.188),iron(r=0.093), manganese(r=0.051), and chemical oxygen demand(r=0.017), and in sampling point 6, the parameters that presented pollution were nitrites(r=0.046), phosphates(r=0.277), iron(r=0.106), and manganese(r=0.190). Finally, findings revealed that agricultural practices in Bishya wetland and surrounding areas, have contributed to the pollution of water quality of Bishya dam through substances of organic manures, chemical fertilizers and pesticides, crop residues, and soil sediments that are transported into the dam by erosion. The study concluded that an effort to create anti-erosions in all areas surrounding wetland, respectful of buffer zones, improving vegetation covers, creating water management bodies at cells level, increasing awareness of population about ecosystem functions, and capturing rainwater from houses may effectively contribute to water quality in Bishya wetland.
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Introduction
Water is a key natural resource, which is very important to all ecosystems on the earth surface (UNESCO, 2006). It is a fundamental element for all forms of life for various purposes such as agriculture, drinking, cleaning, and as shelter for aquatic organisms (Ninhoskinson, 2011). Water covers 70% of the Earth’ssurface, yet 40% of the world’speoples experience water shortage (Mmbando J.et al, 2007). Access to clean and safe water is a basic necessity of human life, and one of the most important global issues (Larsen, 1997). According to WHO, quoted by Mmbando J.et al (2007), 1.4 billion people, equivalent to 20% of the world’spopulation, do not have access to clean and safe water. It is mainly the poorer Less Economically Developed Countries (LEDCs) who have least access. This lack of access is a major barrier to a country’sdevelopment (Mmbando J.et al, 2007). No single measure would do more to reduce disease and saves lives in the developing world than bringing safe water to all (Koffi Annan, 2000). One of the main reasons for the shortage of water is that 97.5% of the water that covers the Earth is saltwater, whilst just 2.5 % is fresh water.
In Africa, up to 90% of freshwater is used in agriculture. The WHO, quoted by Mmbando J.et al (2007), it is estimated that 17% more freshwater will be needed simply to grow enough food to cope with the estimated increase in population. Rapid population growth has put pressure on the world’sresources and affected quality of life. Half of all the populations in LEDCs still do not have safe water to drink. Contaminated water is responsible for the cause and spread of 80% of the world’sdisease including cholera, typhoid and dysentery (WHO, 2006). Waterborne diseases kill 25000 people daily, and about 14 million children under five-year old die each year from illness and hunger (Mmbando J.et al, 2007). Although human beings benefit a lot from water, they are among the main causes of water pollution through poor management of agricultural practices (US-EPA, 1994). These include excessive use of fertilizers for increasing production, traditional irrigation practices, use of pesticides and herbicides and poorly managed animal farming operations (EPA, 2009). The rapid population growth in LEDCs has resulted in environmental degradation and remarkable reduction in cultivable land. Agricultural smallholders dominate the scarce land available and the smaller the land, the more likely the landholder to live in poverty (IDA, 2008). Water management in degraded environment and in avery limited cultivable land is considered as a big challenge for the much-needed expansion of basic services including water services, which cannot be expanded at the desired quality and quantity; thus the need for a new approach to improving water provision in such degraded environment and limited cultivable land (Schreinemachers, 2012).
In Rwanda, the Government has adopted some policies like enhancing irrigation practices, use of fertilizers, expanding the cropland area, increasing use of lime and organic manures, all aim at increasing agricultural productivity and eliminating poverty among citizens (Nahayo et al, 2016). Besides, the Government of Rwanda adopted the National Water Services Strategy through which the Government is committed to fast tracking affordable and sustainable access to safe water in the settlements of both rural and urban areas. This is achievable through defining national standards for low-cost technologies and increasing number of public or communal outlets under formal water service provision (WASAC, 2018). However, these practices adopted for increasing agricultural production have resulted in water quality deterioration through hurrying soil erosion and release of phosphorus, nitrogen and other chemical substances from agrochemicals applied, which in round, cause water pollution and high levels of eutrophication in wetlands and some lakes (REMA, 2009).
Agricultural inputs have been identified as one of the leading sources of water pollution in Rwanda, especially in wetlands (REMA, 2009).The worsening of freshwater quality can be directly observed through water utilities in a country. For instance, the amount spent on acquiring chemicals to treat water constitutes a huge part of any water utility’sexpenditure. The Rwandan Water Utility (WASAC) spends millions of Rwandan Francs on water treatment chemicals wherein 2017/2018 an amount of 96 million Rwandan Francs have been spent for the purification of water in NYANZA town alone (WASAC, 2018). The amount spent on chemicals rises with the deterioration of raw water quality and this in turn makes water expensive, as the water utilities are forced to adjust water prices to recover costs. Some researches related to agricultural policies, crop production have been conducted in Rwanda; however, a challenge of linking these sectors with water quality in order to combat water pollution remains.
Conclusion
Agricultural practices in Bishya wetland and surrounding cropland areas characterized by availability of different crops, ineffective drainage, absence of anti-erosion structures, weak management of wetland margins, absence of vegetation covers, use of organic manures, chemical fertilizers and pesticides, and presence of different types of rocks and soils have influenced water quality in Bishya wetland in all sampling points of Bishya dam as the agricultural inputs were positively correlated with water quality parameters. However, the positive relationship does not mean that all selected parameters have manifested pollution, but some of them did according to RSB guidelines. The parameters that presented pollution were nitrites (r=0.047), Phosphates (r=0.384), Iron (r=0.11), and Manganese (r=0.018) in sampling point P1; in sampling point 2, they were nitrites (r=0.010), Iron (r=0.059), and COD (r=0.012); in sampling point 3, they were pH (r=0.048), nitrites (r=0.086), and phosphates (r=0.329); in sampling point 4, they were nitrites (r=0.123), iron (r=0.182), and Manganese (r=0.051); in sampling point5, Turbidity (r=0.080), nitrites (r=0.095), Phosphates (r=0.188), iron (r=0.093), manganese (r=0.051), and chemical oxygen demand (r=0.017); and in sampling point6, parameters that presented pollution were nitrites (r =0.046), Phosphates (r=0.277), Iron (r=0.106), and Manganese (r=0.190). For sustainable wetland management the researcher suggested the following: To create effective anti-erosions in all areas surrounding Bishya wetland To sensitize people using croplands surrounding Bishya wetland to fully respect the minimum of wetland margins (buffer zone) according to the law on wetland protection applicable in Rwanda, To consider the importance of ecological values of wetlands while developing policies for economic development. To introduce mass education in order to make the population understand well the importance of wetland ecosystem functions. To set up water management bodies at cells level The agricultural policy should not only be focused on the increase in production but also the future use of the wetland. Increase awareness in environmental protection and sustainable management of water resources for farmers in bishya wetland. To capture rainwater from their houses in order to avoid erosion. Respect the laws governing the use of wetland in Rwanda.
