Evaluation of the Effects of Quarrying Operations on Watershed Resources within the Quarrying Sites of Mutonga

Artisanal quarrying supports livelihoods and supplies construction materials, but poorly managed extraction can degrade watershed resources. This study evaluated the effects of quarrying operations on watershed resources within the Mutonga quarrying sites in Meru County, Kenya, focusing on vegetation condition, soil disturbance and river water quality. A mixed-methods research design was adopted, involving 120 respondents selected through purposive and stratified sampling. Data were collected using questionnaires, interviews, participatory rural appraisal, field observations and laboratory analysis of river water samples. Remote sensing and geographic information systems were used to assess vegetation changes through Normalised Difference Vegetation Index analysis for 2015, 2020 and 2025. Quantitative data were analysed using descriptive statistics and chi-square tests. Vegetation conditions deteriorated between 2015 and 2020, while 2025 showed localised recovery alongside continued degradation in intensively exploited areas. Reported forms of soil disturbance included topsoil loss (82%), gully formation (78%) and land surface exposure (74%). Chi-square analysis indicated a significant association between quarrying activities and vegetation degradation. Turbidity increased from 12 NTU upstream to 85 NTU midstream and 72 NTU downstream, while total suspended solids increased from 18 mg/L to 145 mg/L and 128 mg/L, respectively. These patterns suggest localised vegetation disturbance and sediment-related deterioration of river water quality around quarrying sites. The study concludes that quarrying is associated with pressures on interconnected land and water resources. It recommends targeted quarry rehabilitation, riparian vegetation protection, sediment control and sustained watershed monitoring.