▁of ▁the ▁pool ▁is ▁p low ed ; ▁For ests ▁covering ▁ 1 9 5 0   km ² ▁( 1 8 %) ▁are ▁pre val ent ▁in ▁the ▁lower ▁reaches ▁and ▁consist ▁of ▁p ine ▁trees ▁with ▁o ak ▁imp ur ities ; ▁In ▁the ▁upper ▁reaches ▁are ▁broad le aved ▁for ests ▁( o ak , ▁horn be am , ▁map le , ▁ash ), ▁preserved ▁along ▁the ▁s lop es ▁of ▁river ▁valle ys ▁and ▁be ams . ▁In ▁the ▁lower ▁reaches ▁a ▁considerable ▁area ▁is ▁occupied ▁by ▁low - lying ▁re ed ▁b eds ▁and ▁shall ow ▁b ogs , ▁the ▁total ▁area ▁of ▁which ▁is ▁ 1 7 0 0   km ² ▁( 6 %). ▁Some where ▁there ▁are ▁lands ▁covered ▁with ▁me adow ▁veget ation . ▁The ▁la kes ▁in ▁the ▁bas in ▁are ▁very ▁small ▁( 0 . 1 %). ▁The ▁river ▁network ▁is ▁well ▁developed , ▁thanks ▁to ▁the ▁clim atic ▁conditions ▁and ▁the ▁nature ▁of ▁the ▁soil . ▁The ▁density ▁of ▁the ▁river ▁network ▁without ▁taking ▁into ▁account ▁the ▁rivers , ▁up ▁to ▁ 1 0   km ▁long , ▁is ▁ 0 . 2 6 , ▁and ▁the ▁latter ▁account ▁is ▁ 0 . 4 6 . ▁S lop ing ▁and ▁moder ately ▁ste ep ▁s lop es ▁are ▁usually ▁plant ed , ▁ste ep ▁- ▁covered ▁or ▁covered ▁with ▁mixed ▁forest ▁and ▁shr ub . ▁In ▁the ▁lower ▁reaches ▁are ▁mar sh y ▁me adows . ▁ ▁In ▁the ▁upper ▁reaches