2.3.1. Runoff

Total and peak runoff measured at PT (outlet) for 14 storm events were used for model calibration. Manning's *n* back-calculated from discharge measurements was consistent with literature values for "ordinary concrete lining" (0.013) [44] and with the channel condition at PT. Simulated total and peak discharge were then compared and evaluated using the RMSE, which is calculated by the equation below.

$$RMSE = \sqrt{\frac{1}{N} \sum\_{i=1}^{N} (Observed\\_i - Simulated\\_i)^2} \tag{1}$$


Qp × S

0.2963

τ*c*

where *i* is the index of the storm events and '*N*' is the number of events (14).

The selection of the AnnAGNPS model parameters to calibrate the runoff was based on the watershed characteristics, preliminary model runs, and literature values identified for each cell in the watershed [44,45] (Table 2).


**Table 2.** Final AnnAGNPS runoff parameters values used to calibrate runoff.
