Verification of Convergency of the Specific Discharges of Materials Measured at a Small Experimental Forested-Watershed

In the previous paper, the loading rates of TN and TP were measured in Aburahi-S Experimental Forested Watershed (AsEFW; 3.34 ha), and the specific loads (Lss) were evaluated to be 9.95 and 0.168 kg·ha-1·y-1, respectively. The Ls values should be verified to converge within AsEFW in order to be appreciable as parameters characterizing AsEFW. However, it is difficult to install a sufficient number of weirs in such a small watershed to prove directly such convergence. In this paper, water samples of the baseflow were taken up monthly at twelve sites (R0-R7 and L1-L4) located upstream of the weir (R0) of AsEFW for one year. The average concentrations of the nutrients at R0 did not significantly differ (ps values converge within AsEFW. Since springs may affect significantly Ls values, especially in small watersheds, their existence and effect should be checked. A small spring (L5) was found in AsEFW, and its influence on the Ls values of the nutrients was confirmed to be negligible.