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Title: How spatiotemporal variation of soil moisture can explain hydrological connectivity of infiltration-excess dominated hillslope: Observations from lesser Himalayan landscape
Authors: Nanda A.
Sen, Sumit
McNamara J.P.
Published in: Journal of Hydrology
Abstract: This study demonstrated the spatiotemporal variation in runoff generating areas in grassed and agro-forested hillslopes of Lesser Himalaya using soil moisture, soil hydraulic conductivity and rainfall datasets. Nine rainfall events of infiltration-excess dominated hillslopes were analysed and found that only high-intensity rainfall events were able to convert 1–5% of runoff at the outlet. The extremely low patch of soil hydraulic conductivity (<5 mm/h) was located at the outlet in agro-forested hillslope whereas similar low soil hydraulic conductivity patch is located at the end portion in a grassed hillslope. Therefore, the grassed hillslope generated less runoff than the agro-forested hillslope due to its surface resistance and heterogeneity in soil hydraulic conductivity. The runoff generated from the upper part of hillslope re-infiltrated into the middle part due to higher soil hydraulic conductivity. During low and medium intensity rainfall conditions, major runoff contribution was observed from low conductivity zones of the hillslope. Moreover, we analysed the correlation of spatial variation in soil moisture with topographic wetness index (TWI) and soil hydraulic conductivity in two different landuse conditions to examine the predictive potential of these attributes during the wet and dry season. The optimal formulation of TWI was obtained from 72 different combinations using linear mixed effects modelling. The correlation between optimal TWI formulation and soil moisture was found to be negative as the main streamline is located near low conductivity zones. Furthermore, the correlation between TWI and soil moisture is stronger in the dry season than the wet season. In comparison to grass cover hillslope, agro-forested landuse system shows better negative correlation between soil moisture and TWI during the wet season as the agro-forested hillslope produced more runoff than the grassed hillslope. The correlation strength of soil hydraulic conductivity and soil moisture was strongest after mid of the wet season which is directly correlated to the moisture content of hillslopes. © 2019 Elsevier B.V.
Citation: Journal of Hydrology (2019), 579(): -
Issue Date: 2019
Publisher: Elsevier B.V.
Keywords: Data scarce region
Hydrological connectivity
Lesser Himalayan hillslopes
Mixed effects modelling
Soil moisture variability
Topographic Wetness Index (TWI)
ISSN: 221694
Author Scopus IDs: 57201619450
Author Affiliations: Nanda, A., Department of Hydrology, Indian Institute of Technology Roorkee, India
Sen, S., Department of Hydrology, Indian Institute of Technology Roorkee, India
McNamara, J.P., Department of Geosciences, Boise State University, Boise, ID, United States
Funding Details: Authors would like to acknowledge the Science & Engineering Research Board ( SERB ), Department of Science and Technology ( DST ) under grant # SER-776 towards field visits and instrumentation. Authors would also grateful to all the members of research group (especially Dr. Vikram Kumar and Ravi Meena) for their support during installation and field visit and Dr. Ajanta Goswami and his research group from Department of Earth Science for help during field survey of 0.5 m resolution digital elevation model preparation. Moreover, authors are thankful to all the local field persons of Aglar watershed. First author would like to thank Ministry of Human Resource Development ( MHRD ), India for providing fellowship during PhD programme.
Corresponding Author: Sen, S.; Department of Hydrology, Indian Institute of Technology RoorkeeIndia
Appears in Collections:Journal Publications [HY]

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