Small mid-field water reservoirs are multifunctional ecosystems occurring as isolated elements within agricultural landscapes and highly susceptible to external pressures. Although they are often treated as uniform systems, evidence for fine-scale spatial heterogeneity remains limited. This study examined two adjacent mid-field reservoirs in south-eastern Poland, embedded in an intensively used agricultural area. The aim of the study was to assess the ecological value of the reservoirs and to determine how shoreline land use and riparian buffer-zone structure affect floristic diversity and selected physical and chemical parameters of surface water and shallow groundwater. Investigations were conducted at four sites representing contrasting shoreline management types. Water quality, nutrient concentrations, vegetation composition and land-cover characteristics were analysed using standard methods. Despite their small size and close proximity, the reservoirs showed pronounced spatial variability in water quality and vegetation structure. Shoreline sections exposed to intensive agriculture and steeper slopes were associated with higher nitrate and phosphate concentrations and lower plant diversity, whereas sites bordered by dense shrub and tree buffer zones exhibited lower nutrient levels and higher floristic diversity. These results demonstrate that small mid-field reservoirs cannot be regarded as homogeneous systems and confirm the key role of buffer zones in shaping their ecological condition, providing practical guidance for the design and management of vegetated buffers in small agricultural catchments.