Study on the Relationship between Precipitation and RiverWater at BalangMountainWatershed inWolong Nature Reserve of Sichuan Province

The authors investigated hydrogen and oxygen stab le iso tope ( δD and δ18O ) ofw ater in Pit iao R iver, and compared them w ith the δD and δ18O of precipitation atWolong Nature Reserve o f Sichuan Prov ince to explore the relation-ship betw een riverw ater δD and δ18O. Itw as found that thewater δD w as positively correlated w ith water δ18O, name ly,δD = 3. 888 -18O - 45. 614 ( R2 = 0. 494, p 18O and δD in the riverwaterweremuchsam ller than those in the precipitation. The excess deuterium ( d) in the river water and in the precipitat ion show ed avery smi ilar patterns o f the seasonal variat ion, w ith the h igher values in w inter than in summer. Snow and snow-icemelting w ater discharg ing into the river variedw ith seasons and th is process occurredmainly from November to nex t June. Theresponse tmi es of δ18O and δD in the riverw ater to precipitation depended on the intensity of prec ipitation. G iven the intensities of precipitation at 0~ 10mm, 10~ 20 mm and 20~ 30 mm, the response tmi es o f δD and δ18O in the river w aterw ere 3 d, 2 d, and 1~ 2 d, respectively, after the occurrence of prec ipitat ion. This suggested thatw ell-structuredsub-a lpine dark brown coniferous forests could mi prove rain w ater permeab ility into so il and facilitatew atermovement intothe adjacent rivers, byw hich the forest regulated the run-off process and w ater discharge into the river.