Dissolved organic carbon (DOC) in water discharged from agricultural land is one of the indicators of waterpollution. As aromatic compounds, which is the main component of DOC, absorb light in the UV-visibleregion, the intensity of UV-visible absorbance is correlated with DOC concentrations in water. In this study, aregression equation between DOC concentration of reference samples (n = 12, extracts of manure composts)and UV-visible absorbance was established. The applicability of the established equation was tested usingwater samples (n = 44) collected from a rural watershed in Jeonnam, South Korea. The peak absorbance ofDOC in the compost extracts was detected at 275 nm, and was positively correlated (R2= 0.99, P < 0.001) withDOC concentrations. Although the DOC concentrations of water samples determined using the equation werelower than those measured by TOC analysis by about 15%, the estimated DOC concentrations were strongly(R2= 0.96, RMSE = 0.97, P < 0.001) correlated with measured DOC concentrations. Our study suggests thatthe DOC concentrations of watershed can be estimated by measuring the UV-visible absorbance method.