Department of Geography and Environmental Studies, Stellenbosch University, Stellenbosch, South Africa.
Department of Earth Science, Stellenbosch University, Stellenbosch, South Africa.
Environ Monit Assess. 2022 Dec 6;195(1):177. doi: 10.1007/s10661-022-10776-4.
Transformation of natural vegetation to cultivated fields has resulted in marked increases in water quality degradation and nutrient loading of rivers globally. In many developing countries, monitoring and evaluating the impacts of agriculture on water quality are limited by financial constraints and focus is given to large water bodies. This paper presents and discusses the results of a year-long monitoring of a typical river system in an agricultural setting, namely the Bot River, Western Cape, South Africa. Results show seasonal increases in N concentrations and SRP driven by surrounding agricultural activities. Water chemistry and changes to nutrient loads were found to be site specific, which demonstrates that monitoring programmes focussing on one or two sites are not representative of the entire catchment. Monitoring and reporting of small river systems are thus un(der)-represented in large databases such as the UN Global Environment Monitoring System for Freshwater (GEMS/Water) programme. The results highlight the importance of selecting appropriate and representative monitoring sites for these rivers when budgetary constraints limit the number of points that can be monitored sustainably. The findings should also be applicable to similar catchments in the Western Cape and beyond as they demonstrate the magnitude of seasonal nutrient fluxes in the system.
自然植被向耕地的转化导致了全球范围内水质恶化和营养物质负荷增加。在许多发展中国家，由于资金限制，对农业对水质的影响的监测和评估受到限制，重点放在大型水体上。本文介绍并讨论了对南非西开普省典型河流系统（即 Bot 河）进行为期一年的监测结果。结果表明，周围农业活动导致 N 浓度和 SRP 呈季节性增加。发现水化学和养分负荷的变化具有特定地点的特征，这表明仅关注一两个地点的监测计划不能代表整个集水区。因此，在诸如联合国全球环境监测系统淡水（GEMS/Water）计划等大型数据库中，对小河系统的监测和报告都没有得到充分体现。这些结果强调了在预算限制限制可持续监测的点数时，为这些河流选择合适和有代表性的监测点的重要性。由于这些结果表明了系统中季节性养分通量的大小，因此它们也应该适用于西开普省及其他地区的类似集水区。
