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Landscape pattern effects on surface runoff: Assessment using a hydrologic model in the Fuhe Basin of Poyang Lake Watershed
* 1 , 2 , 2 , 1
1  State Key Laboratory of Information of Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China
2  School of Urban and Environment Sciences, Central China Normal University, Wuhan 430079, China


A series of urgent issues such as global warming, frequent natural disasters, and water shortages are largely result from heavy human interference and its induced changes of landscape structure. How the landscape pattern variation impacts the surface runoff remains an unsolved issue for watershed water management. In the past decades, the action of ecological environment protection and projects of returning farmland to forests and grasslands have significantly changed the landscape pattern in Fuhe Basin of Poyang Lake watershed, which will inevitably affect the hydrological cycle of the basin. In this study, the SWAT (Soil and Water Assessment Tool) model for the Fuhe Basin was firstly built to predict the runoff depth for the divided 31 subbasins during three periods from 1990 to 1999, 2000 to 2008 and 2009 to 2013. Meanwhile, dynamic changes of landscape pattern were analyzed Based on the land use and cover data in the year of 1990, 2000, and 2008. Finally, the correlations between different landscape indicators and surface runoff were quantified over subbasins using Spearman Correlation analysis.

Results showed that the SWAT model is applicable in Fuhe Basin with R2 (correlation coefficient) and Ens (Nash-Sutcliffe efficiency coefficient) larger than 0.85 for runoff prediction. Based on the land use and cover data in the year of 1990, 2000, and 2008, the landscape index were calculated. The fragmentation degree increased first and then decreased during the two transition periods. The landscape patches shape became more complicated and connectivity of different landscapes decreased and then increased, among which the forest and paddy field have greatest fragmentation degree. Forest has a larger dominance degree, which was highly connectable to patches of other various types of landscape. According to the changes of landscape pattern from 1990 to 2008, the smaller fragmentation degree, more complex patch shape, and more uneven distribution of landscape patches led to more precipitation interception and runoff reduction.

From the perspective of the landscape type, the landscape area ratio (PLAND) of dry land, paddy field, water area, urban and rural construction land patches has a significantly positive correlation with surface runoff, while PLAND and FRAC_AM (Area Weighted Patch Fractal Dimension) index of forestland have a significantly negative correlation with surface runoff. The complexity of forestland patch shape strengthened the interception of rainfall and plant transpiration of land surface, which would reduce water yield. The expansion of urban impervious area, aggravating landscape fragmentation, reduced runoff interception and increased surface runoff, which can be indicated by positive relation with PLAND and FRAC_AM index of urban construction. Deeply understanding surface runoff alternations, induced by landscape patterns changes, would provide theoretical support for solving the problems of sustainable utilization of water resources, but also offers best management practices (BMPs) for land management.

Keywords: landscape pattern; landscape index; surface runoff; hydrologic modelling; Fuhe Basin of Poyang Lake
Comments on this paper
Bojan Đurin
Comment - Bojan Đurin, University North, Croatia.
Very detailed analysis. Here is my question number 1:
Can you explain why you have split original time serie into three subparts, as well as on which criteria?

• Increasing during 1990–1999
• Decreasing during 2000–2008
• Fluctuation during 2009–2013

I would like to hear more detailed analysis.
Jianzhong Lu
Thanks for your interests in our work. The entire study period was divided into three parts depending on the accumulation curve of annual runoff anomaly of Fuhe River basin during 1990 to 2013, showed in the slides. The annual mean runoff is 137,800 m3/s in the basin over these 24 years, and the runoff anomaly was calculated for each year. From the figure, we find that the annual runoff exhibit the three patterns. The runoff shows an increasing trend during 1990 to 1999, then decreasing trend during 2000 to 2008, while an fluctuation trend during 2009 to 2013. we also considered the landscape data we have collected in the year 1990, 2000 and 2008 which are the boundaries of three divided periods. It would help us to analyze impacts of landscape pattern changes on surface runoff with corresponging time range. The full paper will be coming soon. Thanks for your attention.

Bojan Đurin
Reply on author's comment/answer
Thank you for your reply. Such analysis are my favorite. Usually, when I have some time series, I apply Rescaled Adjusted Partial Sums (RAPS) method, which gives me insight into possible subseries, which can not be seen at first. What do you think about it, i.e. your opinion about applying RAPS into your research?
Jianzhong Lu
Thanks for for your suggestion. Maybe we would like to learn more about RAPS method and have a try on it.

Bojan Đurin
Reply No2 on author's comment/answer
This method, which is not complicated, in your case could be used to confirm there three subseries, or even to find possible subseries in every of three subpart series, which could lead to maybe new conclusions. Please, see my paper:
Impact of Seasonal Changes of Precipitation and Air Temperature on Clay Excavation
I would be happy if you try it and tell me what you have obtained.