We explored the potential of the environment and disaster monitoring and forecasting small satellite constellations (HJ-1A/1B satellites) charge-coupled device (CCD) imagery (spatial resolution of 30 m, revisit time of 2 days) in the monitoring of total suspended sediment (TSS) concentrations in dynamic water bodies using Poyang Lake, the largest freshwater lake in China, as an example. Field surveys conducted during October 17-26, 2009 showed a wide range of TSS concentration (3-524 mg/L). Atmospheric correction was implemented using the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) module in ENVI with the aid of aerosol information retrieved from concurrent Terra/Moderate Resolution Imaging Spectroradiometer (MODIS) surveys, which worked well at the CCD bands with relatively high reflectance. A practical exponential retrieval algorithm was created between satellite remote sensing reflectance and in-situ measured TSS concentration. The retrieved results for the whole water area matched the in-situ data well at most stations. The retrieval errors may be related to the problem of scale matching and mixed pixel. In three selected subregions of Poyang Lake, the distribution trend of retrieved TSS was consistent with that of the field investigation. It was shown that HJ-1A/1B CCD imagery can be used to estimate TSS concentrations in Poyang Lake over synoptic scales after applying an appropriate atmospheric correction method and retrieval algorithm.
The Soil and Water Assessment Tool(SWAT)model was used to assess the impacts of different land use scenarios on hydrological processes in the Fuhe watershed in Poyang Lake Basin,East China.A total of 12 model parameters were calibrated with observed monthly runoff data for 1982-1988 and validated for 1991-1998 for baseline conditions.The baseline test results of R2 and Nash-Sutcliffe model efficiency(NSE)values ranged between 0.88 and 0.94 across the calibration and validation periods,indicating that SWAT accurately replicated the Fuhe watershed streamflow.Several different land use scenarios were then simulated with the model,focusing on the impacts of land use change on the hydrology of the watershed.The results of hypothetical scenario simulations revealed that surface runoff declined while groundwater recharge and evapotranspiration(ET)increased,as forest land,agriculture land and/or grassland areas increased,as well as when paddy field and urban areas decreased.These results further showed that forest land has a higher capacity to conserve the water as compared to pasture land.The results of the real scenario simulations revealed that urbanization is the strongest contributor to changes in surface runoff,water yield,and ET.Urbanization can be considered as a potential major environmental stressor controlling hydrological components.
Tao CanChen XiaolingLu JianzhongPhilip W.GassmanSauvage SabineSanchez Pérez José-Miguel
