Baltimore Ecosystem Study Institute of Ecosystem Studies

2015 BES Annual Meeting Presentation and Poster Abstracts

Effects of Land-use Pattern and Hydrological Regime on Riverine Nitrogen Export in a Coastal Watershed of Southeast China
Huang, Jinliang
Co-Authors: Jinliang Huang, Yaling Huang, Ayu Ervinia, Panpan Zhao

Abstract: Over the past several decades, many regions of the world have experienced large increases in riverine nitrogen (N) fluxes to coastal waters, leading to eutrophication in catchment-coast continuum, thereby posing a threat to the local/regional water security and ecosystem service supporting. Long-term historical data collection, In-situ monitoring, watershed modeling, and geospatial techniques were performed in this study to explore the coupled effects of land-use pattern and hydrological regime on nitrate export in Jiulong River watershed (JRW), which supplies water for approximately ten million residents, households industries, and irrigation purposes. Surface water samples of baseflow were collected from 17 headwater sub-watersheds which were classified into three types of watersheds (natural, urban and agricultural) in the flood, dry and transition seasons during six consecutive years (2010-2015). Hydrological Simulation Program--Fortran (HSPF) model was applied to estimate daily discharge for ungauged sub-watersheds so as to estimate the nitrogen flux from headwater sub-watersheds. The results showed that nitrate concentrate increased 30 times from 1961 to 1998 and annual riverine nitrate export increased exponentially from 169 to 26034t N/a during the period over 1961-2013. Nitrogen had the highest mean concentrations in the dry season, whereas the lowest concentrations were in the flood season. The concentration of ammonia was generally higher in urban watersheds than those in natural and agricultural watersheds while nitrate were generally higher in agricultural watersheds than those in urban and natural watersheds. The annual loadings of total nitrogen for three types of watersheds with different predominant land use type in JRW were in the following order: agricultural > urban> natural. Further study would be carried out to gain better understanding on the interactive impacts of land-use and climate changes on riverine nitrogen export by comparing our work with the studies at Baltimore Long- term ecological site.