# Hydrological Analysis of Extreme Rain Events in a Medium-Sized Basin
## 3 Results
The _BETA_ parameter was also greater in the case of the semi-urban sub-basin compared to the urban one, especially regarding the forests' and croplands' zones, but in the urban areas, the parameter obtained similar values in both sub-basins. The maximum _PERC_ rate was greater in the most rural sub-basins and lower in the urbanized, semi-urban and urban ones, as expected. The _UZL_ threshold value for the groundwater \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & W1460 & W790 & W800 & W900 & W1030 & W1020 \\ \hline _TT_ (\({}^{\circ}\)**C**) & \(-\)0.5 & \(-\)0.5 & \(-\)0.5 & \(-\)0.5 & 0 & 0 \\ _CFMAX_ (mm/h \({}^{\circ}\)**C**) & 0.15 & 0.15 & 0.15 & 0.15 & 0.15 & 0.15 \\ _SP_ & 1 & 1 & 1 & 1 & 1 & 1 \\ _SFCF_ & 0.7 & 0.7 & 0.9 & 0.9 & 1 & 1 \\ _CFR_ & 0.05 & 0.05 & 0.05 & 0.05 & 0.05 & 0.05 \\ _CWH_ & 0.1 & 0.1 & 0.1 & 0.1 & 0.1 & 0.1 \\ _FC_ (mm) & 495 & 495 & 495 & 120 & 120 & 115 \\ _Forests and_ & _LP_ & 0.1 & 0.1 & 0.1 & 0.75 & 0.75 & 0.775 \\ _BETA_ & 2.75 & 2.95 & 3.55 & 1.25 & 1 & 2.15 \\ _FC_ (mm) & 490 & 490 & 490 & 100 & 80 & 95 \\ _Croplands_ & _LP_ & 0.105 & 0.105 & 0.105 & 0.775 & 0.8 & 0.8 \\ _BETA_ & 3.15 & 3.75 & 3.95 & 1.35 & 1.05 & 2.25 \\ _FC_ (mm) & 90 & 85 & 65 & 55 & 40 & 50 \\ _Urban_ & _LP_ & 0.4 & 0.85 & 0.2 & 0.9 & 1 & 0.825 \\ _BETA_ & 3.45 & 3.95 & 4.75 & 2.5 & 2 & 2.275 \\ _PERC_ (mm/h) & 0.3 & 0.325 & 0.215 & 0.25 & 0.05 & 0.2 \\ _UZL_ (mm) & 9.5 & 5.5 & 1.45 & 1.75 & 2 & 12.5 \\ _K0_ (I/h) & 0.3 & 0.135 & 0.1 & 0.1 & 0.3 & 0.25 \\ _K1_ (I/h) & 0.01 & 0.0145 & 0.001 & 0.0015 & 0.165 & 0.001 \\ _K2_ (I/h) & 0.004 & 0.0035 & 0.015 & 0.045 & 0.04 & 0.0015 \\ _MAXB_/**3** & 22 & 16 & 15 & 15 & 5 & 16 \\
**28-30 May 2013 NSE** & 0.8378 & 0.8673 & 0.6331 & 0.8334 & 0.8320 & 0.7096 \\
**4–10 July 2013 NSE** & 0.8101 & 0.7893 & 0.7580 & 0.8157 & 0.9014 & 0.9086 \\ \hline \hline \end{tabular}  
* Notes: _TT_ (\({}^{\circ}\)C) is a threshold air temperature over which precipitation is assumed not to be snow but rain, _CFMAX_ (mm/h \({}^{\circ}\)C) is a degree-hour factor for the estimation of snowmelt, _SP_ is a seasonal variability in the degree-hour factor, _SFCF_ is a snowfall correction factor counterbalancing errors on snowfall assessment by the model and evaporated water from snowpack, _CFR_ is a refreezing coefficient of water inside the snowpack in case temperature falls under the threshold, _CWH_ is a retention coefficient of melted snow and rainfall in the snowpack, _FC_ (mm) is the maximum water content of the soil box, _LP_ is a threshold value for actual evaporation reaching potential evaporation, _BETA_ is a parameter controlling the relative contribution of rain or snowmelt to flow discharge, _PERC_ (mm/h) is the maximum percolation rate from the upper to lower groundwater box, _UZL_ (mm) is a threshold value for groundwater content, _K0_ is the recession coefficient for upper groundwater box, _KI_ is the recession coefficient for intermediate groundwater box, _K2_ is the recession coefficient for lower groundwater box, and _MAXB_AS (h) is a runoff transformation parameter specifying the routine time length in a triangular weighting function.  
\end{table} 
Table 10: Optimal values’ parameters via calibration of the HBV-light (a recent version of Hydrologiska Byárans Vattenbal-anasvadeling) model for the events of 28–30 May 2013 and 4–10 July 2013.  
content responsible for outflow was greater in the rural than in the urbanized sub-basins, however, in semi-urban and urban sub-watershers, it did not follow a similar trend. In all the sub-basins, the _K0_ coefficient was greater than _K1_ and _K2_, indicating that recession was more considerable in the upper groundwater box than in the intermediate and lower one. _K1_ was higher than _K2_ in W1460, W790, and W1030, smaller in W800 and W900, whereas it was similar in W1020. The Nash-Sutcliffe coefficient was very good for the sub-basins of the 28-30 May 2013 event, apart from the sub-basin W800 in which it was satisfactory, and W1020 where it was good.