Variation Of Hydrological Regimes And Its Driving Forces Of Naolin River Since1950s

Climate change and human activities have been the main driving forces forhydrological regime variations on local scale; especially the influences on land usechange on runoff fluctuation are greater than natural factors at basin level. In thepresent work, Naoli River Basin in Sanjiang Plain, Northeast China, were chosen asthe study area, and runoff variation in the past more50s years had been studied basedon long-time monitoring data of water flow and integrating GIS, remote sensing,theories and methods in Landscape Ecology. Runoff changing rules were revealed anddriving forces of land use change and landscape patterns on runoff were discussed.We also estimated preliminary the supplying abilities of eco-environmental water inNaoli River Basin. Some conclusions are gotten as followed:In the recent50years, annual average runoff of four hydrological stations,bao'an (BA), baoqing (BQ), caizuizi (CZZ) and Hongqiling (HQL) station, showed andecreasing trends with different rate, of which the lowest rates was found in HQL.Compared with runoff in1957, runoff in2009of BA, BQ and CZZ had decreased by64.1%,76.3%and84.3%, respectively. In the past50years, seasonal runoff in BA,BQ and CZZ was in decreasing, of which was significant in spring, summer andautumn.Runoff variation ratios (K) of Naoli River had been decreasing during1955-2009.in the four hydrological stations, numbers of years of K<1accounted for about51.7%~64.0%, and yeas of K<1mostly concentrated after1970s. Numbers of wetyears were much less than dry years. Circulation periods of wet to dry years hadchanged and frequencies of wet years decreased while appearing periods appeared,and frequencies of dry years rise greatly, from25.0%~27.8%to83.9%~87.5%.Annual runoff variation amplitudes were increasing and showing that risks of thearidity and flood disaster increased. Asymmetry of runoff in a year increased andwater resources concentrated in special month more and more. M-K test indicated thatrunoff trend was in decreasing in the past50years, while the revulsion occurred in themiddle and late1960s and reached to significant levels in middle-late of1970s andthe early1980s. During1954-2005, Characteristics of land use in Naoli River were farmland andconstructed areas increasing inverse forestland, grassland, water areas and unusedland decreasing in different scopes with the decreasing rate of25%,70%,2%, and82.9%, respectively, of which the most decreased among unused land was marsh andmost of them were converted into farmland. During1954-2005, landscape matrixes ofNaoli River basin had changed greatly, and farmland had been the main landscape.Landscape complexities in Naoli River basin decreased, have been becoming singleand simple.Runoff of Naoli River basin showed a remarkable decreasing trends withreclamation time, which could be divided into three stages. The first was1957-1977,the secondary was1977-1992and the third was1992-2005. Runoff of BA, BQ andCZZ stations differed in different in different reclamation time. In the sub-watershed,relationships between runoff variations with rations between different land types weredifferent. On the whole, ratios between farmland and forest, between farmland andgrassland were not significantly related to runoff variations, while ratios betweenfarmland and unused land were closely with runoff. In the four hydrological stations,runoff firstly increased and then decreased with the increasing of ratios betweenfarmland and unused land. Besides the land use change, increasing of channels inNaoli River basin had resulted in the seasonal runoff changing significantly in CZZstation. The construction of Longtouqiao reservoir had decreased the runoff in BQ by47%. Since1950s, contributions of runoff change and human activities on runoffdecreasing were48.60%and51.40%in BQ station, and38.37%and61.63%in CZZstationIn2005, the total eco-environmental water requirement amount was603.22mm,and the precipitation was275.36mm. There was about127.86mm water gap if otherwater requirement was not considered. This indicated that water requirement was notmet only depending on natural precipitation in Naoli River.