Stream Runoff And Hydrochemical Characteristics Of Forest Watershed In Greater Xing’an Mountains

Six forest streams in the north of Grater Xing’an Mountains were selected and set seven observation sections to study the hydrochemical characteristics of streams. On Christmas Village Section, Lao Gou Forest Farm Section and Xiao Beigou Section, used water level loggers and cup-type current meters to study the runoff characteristics. The results show that: the water of most streams was weak alkaline, low salinity and soft. The averages of pH, total hardness and TDS were7.69,73.49mg/L and100mg/L respectively. The water quality was generally good. The total runoff depth in the observations period was34.23to162.60mm, which was closely related to the proportion of larch and basin size. When precipitation was more than9.0mm and less affected by the early rain, runoff began to respond obviously. The time to start growing of runoff was close that the longest interval was only3.0h. When the precipitations were different significantly, the runoff was increased with the precipitation. When the precipitation was9.3mm, the increment of runoff was0.03to0.25m3/s. It could be0.19to3.16m3/s when the precipitation was81.7mm. When the precipitations were similar, the variations of runoff mainly depended on the early rains and the saturation of soil and litter layer. The major anions in the stream water were F-, Cl-, NO3-and SO42-. The major cations were K+, Ca2+, Na+and Mg2+, and the content of most streams were Ca2+>Mg2+>Na++K+. Compared to those of the precipitation, the migration types of K+, Ca2+, Na+, Mg2+, SO42-, F-and Fe content were leaching, while that of Cl-, NO3-, Zn2+and Pb2+were storage. The migration trend of Mn was not obvious. The major materials may affect the chemical composition of streams were CaSO4and MgSO4. The content of Ca2+and Mg2+were positive correlation in most basins. It showed that the two ions may have a same source. But the eluviations of rainfall to Ca2+、 Mg2+in the forest ecosystem rain was limited. When this effect reached the upper limit, increasing runoff would dilute the content of Ca2、Mg2+.20%broadleaf species were replaced by Pinus sylvestris during the migration from upstream to downstream of Lao yeling stream. Meanwhile the pH value and the content of Fe, Mn and Na+increased1.88%to132.22%, but TDS, NO3-and Mg2+decreased36.75%to83.33%. It showed that Pinus sylvestris has a certain effect on the above ingredients.