Figure 6. Landcover map in the Tyrma region as a result of extrapolating the decision-tree’s classification model. Orange areas denote the places classified into wetland (Mari ). Similarly, green areas denote forest, and purple areas denote grassland. Areas enclosed by color and black lines show the catchment areas of the sampled rivers.
3.2 River water chemistry (dFe, DOC, EC) and their relationship with the coverage percentage of wetland (Mari ) in the watersheds.
Using the produced landcover map (Figure 6), the coverage percentage of wetland (Mari ) in the sampled river watersheds was calculated. This result is shown in Table 1 with the results of dFe, DOC, and EC. The range of dFe concentration in the five large rivers was 0.12–0.38 mg L–1, with dFe being especially high in the Yaurin and Gujik Rivers. The range of DOC concentration was 13.4–19.0 mg L–1, and similar to dFe, DOC concentration was higher in the Yaurin and Gujik rivers than in other large rivers. EC in the large rivers was low on average and its range was 3.90–5.63 mS m–1. The range of wetland coverage was relatively high in the Gujik Basin at 34.8%, but there was no significant difference among other large rivers of 14.7–16.5%. Alternatively, the small rivers showed more variety of water chemistry compared with the large rivers: they showed quite wide ranges for dFe concentration of 0.02–0.54 mg L–1 and DOC concentration of 7.4–29.5 mg L–1. EC in the small rivers was also in a wide range of 2.89–14.00 mS m–1. The coverage of wetland in the small river watersheds was 1.5–55.9%, especially higher in the rivers of the Tyrma River system (Rivers 9–19 in Table1) than those of the Gujal River system (Rivers 1–8 in Table1).