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The measurement of greenhouse gas (GHG) fluxes in estuaries is crucial in expressing the impacts of these GHGs on global warming, and hence climate change. In this study, we investigated the effect of various environmental and micrometeorological factors on diurnal and seasonal variations of methane (CH 4) and carbon dioxide (CO 2) in a tidal inundated saltmarsh. Measurements of GHG fluxes were taken by using eddy covariance technique from August 2015 to July 2016 in Tomago wetland, Newcastle, NSW, Australia. In this paper, a positive flux is defined as the one directing into the atmosphere. The highest average diurnal emissions were 2.54 µg m-2 s-1 CH 4 during the day and 0.45 mg m-2 s-1 CO 2 at night. Monthly average fluxes peaked in February (0.365 µg m-2 s-1 CH 4 and 0.137 mg m-2 s-1 CO 2). There was a significant negative relationship between CO 2 flux and water level (p < 0.001), tidal height (p = 0.02) and positive relationship with water temperature (p = 0.002). CH 4 flux showed positive correlation with water level and negative correlation with EC although not statistically significant. Although tidal flooding did not demonstrate clearly carbon sequestration before and after tidal reinstatement, freshwater events (rainfall) were seen to influence the wetland carbon balance.

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Abstract:The statistical characteristics of a hydrological data for the purposes of decision making in water resource planning and management is only justifiable if the data has the right attributes. This requires that the data being analysed are consistent, free of trend and being part of a stochastic process whose random characteristics is described by an appropriate distribution hypothesis. The data available for statistical analysis had a lot of missing values which could not be ordinarily filled but required a more comprehensive approach to fill these missing values. The KSOM (Kohonen Self-organising Map) was used to fill the missing runoff data from the Jidere-Bonde, Lokoja and Makundi river sites in the Niger basin. Results from the studies have shown that KSOM is the best tool for filling hydrological data with high number of missing values. After the data had been processed, some statistical applications were used to establish the runoff time-series characteristics of the three river sites of the Niger River basin. The results showed good attributes for all three river sites, except that Jidere River's data exhibited inconsistency. The presence of trend was also established for all three river sites; Jidere River was modelled based on 3-parameter lognormal, the other two river sites were modelled based on normal distribution probability. The presence of trend and other attributes require that a more stochastic modelling process be carried out. However, the results established give reference for water resource planning and management.