## 4 Results  
The main characteristics of the twenty-six (26) evaluated points located in the main contributors and soil deposits near to the rivers and tributaries of the Alhajuela sub-basin are described in Table 2.  
Table 3 shows the results of the determinations of the isotopic ratios of the carbon chain fatty acids (C14 to C34) for each sampling point (PAN-F01 to PANF-10 being sources; PAN-M01 to PAN-M16 being mixtures), providing fundamental information for applying the CSSI technique. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Point**} & **Coordinate E (UTM)** & **Coordinate N (UTM)** & **Elevation (m)** & **Observation** & **Code** \\ \hline
1 & Escandalosa & 656036 & 1042035 & 489 & upper part & PAN-F01 \\ \hline
2 & Esperanza & 680898 & 1040569 & 552 & upper part & PAN-F02 \\ \hline
3 & Chamón & 684799 & 1033081 & 656 & upper part & PAN-F03 \\ \hline
4 & San Miguel & 664225 & 1041656 & 532 & upper part & PAN-F04 \\ \hline
5 & Dos Bocas & 672246 & 1045265 & - & upper part & PAN-F05 \\ \hline
6 & Chagresito & 686106 & 1039070 & 461 & upper part & PAN-F06 \\ \hline
7 & Quebrada Ancha River & 658502 & 1029911 & 94 & lower part & PAN-F07 \\ \hline
8 & Boquerón River & 657947 & 1037415 & 104 & upper middle part & PAN-F08 \\ \hline
9 & La Fea River & 661522 & 1022680 & 128 & lower part & PAN-F09 \\ \hline
10 & Chagres River CH1-2 & 662895 & 1023605 & 74 & upper middle part & PAN-F10 \\ \hline
11 & Indio Este River & 661468 & 1019588 & 75 &
\begin{tabular}{c} INE-1 \\ river mouth \\ \end{tabular} & PAN-M01 \\ \hline
12 & Chagres River CH1-0 & 662957 & 1024333 & 114 & middle part & PAN-M02 \\ \hline
13 & Chagres River CH1 & 661670 & 1020488 & 72 & CH-1 & PAN-M03 \\ \hline
14 & Chagres River CDL-2 & 661239 & 1035829 & 78 & CDL-2 & PAN-M04 \\ \hline
15 & Boquerón River & 658493 & 1034183 & 72 & PEL-3 & PAN-M05 \\ \hline
16 & Candelaria & 662870 & 1037590 & 90 & CDL-1 & PAN-M06 \\ \hline
17 & Quebrada Bonita & 653470 & 1032773 & 101 & lower part & PAN-M07 \\ \hline
18 & CDL-3 & 659219 & 1034420 & 70 & CDL-3 & PAN-M08 \\ \hline
19 & Vistamares & 675625 & 1021547 & 944 & - & PAN-M09 \\ \hline
20 & Santa Librada & 659803 & 1041130 & 136 & - & PAN-M10 \\ \hline
21 & Guarumal & 662593 & 1017814 & 119 & - & PAN-M11 \\ \hline
22 & INE-3 & 675109 & 1017504 & 592 & upper part & PAN-M12 \\ \hline
23 & Santo Domingo & 653844 & 1036192 & 466 & upper part & PAN-M13 \\ \hline
24 & La Palma River & 662709 & 1022661 & 107 & lower part & PAN-M14 \\ \hline
25 & Monocongo River & 659952 & 1033962 & 90 & lower part & PAN-M15 \\ \hline
26 & Benitez River & 657478 & 1024878 & 114 & lower part & PAN-M16 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: CSSI points sampled in Alhajuela sub-basin. For the application of the CSSI technique, it is essential to link the sampling points with zones representative of the predominant land uses in the study area that will allow us to subsequently determinate the contributions of the sources in the different mixing points identified. To obtain detailed information on soil contributors in the study area, the different historical land uses reported for the region were processed using GIS tools and information downloaded from public databases [20], as shown in Figure 7 and reviewed and verified on the field studies. A first analysis identified 10 sampling points as sources, associated with three (3) different land uses, four (4) rivers and other contributors where samples were taken. These soil contributors identified were \"mature mixed broadleaf forest\" in 60% of the sampled points, \"water surface\" in 20%, and finally \"pasture\" in 20% of the samples (Table 4). Mature mixed broadleaf forest (re-labeled as **Forest**) covers more than 90% of the Alhajuela sub-basin, **Pasture** 4%, and water surface 4%; the remaining 2% is associated with population and other minor land uses. The water surface was also re-labeled as **Sediment**.