Scaling approaches to the modelling of water, sediment and nutrient fluxes within semi-arid landscapes, Jornada Basin, New Mexico

TitleScaling approaches to the modelling of water, sediment and nutrient fluxes within semi-arid landscapes, Jornada Basin, New Mexico
Publication TypeThesis
Year of Publication2004
AuthorsMüller ENora
Number of Pages271
Date Published2004
UniversityKing's College London, University of London
Accession NumberJRN00419
Call Number00919
Keywordsdissertation, hydrology, creosotebush, hydrology, ecosystem dynamics, hydrology, grassland, hydrology, model, hydrology, nutrient fluxes, hydrology, nutrient transport, hydrology, overland flow, hydrology, overland-flow model, hydrology, processes, hydrology, remote sensing, hydrology, sediment fluxes, hydrology, sediment transport, hydrology, sheet flow, hydrology, shrubland, hydrology, stock tanks, hydrology, surface runoff, model, hydrology, thesis
AbstractOverland flow generated by high-intensity rainstorms has been suggested as having an important role in desertification, resulting in a significant vegetation change from productive grassland to desert shrubland in the southwestern part of the United States. For the quantification of overland flow and associated nutrient and sediment fluxes, there are significant scale issues involved that require resolution. To address these issues, a fieldwork-integrated modeling approach was employed to enable the quantification of water, sediment and nutrient fluxes within and between shrubland and grassland associations in a semi-arid ecosystem, Jornada Basin in the Chihuahuan Desert, New Mexico. This thesis is the evaluation of scaling approaches to the numerical modeling of these fluxes combined with the appropriate application of scaling tools for model parameterization. Special emphasis is placed on the investigation of parameter and process scaling and the applicability of scaling tools to interpolate and extrapolate field data, disaggregate remotely sensed data and aggregate model parameters. Extensive field studies were carried out to acquire detailed understanding of the spatial distribution of hydrological, soil- and nutrient-related model parameters within black gramma grassland and creosote, tarbush and mesquite shrublands. The statistical and geostatistical analysis of the field data resulted in the development of scaling techniques that enable the spatially realistic reproduction of the small-scale variability and connectivity features of model input parameters. Spatially distributed, process-orientated models with a 2-m resolution were employed to enable an adequate representation of model input parameters and an appropriate reproduction of overland flow characteristics and sediment- and nutrient-transport processes. Based on these results, the models were upscaled to a resolution of 10-m under specific evaluation of process and parameter scaling issues. The upscaled model versions were then employed for the flex quantification within and percentage change in fluxes between shrubland and grassland associations. The modeling studies provided important insights into stability of grassland-shrubland boundaries as a function of nutrient depletion and water-resource enrichment for the grassland by the action of overland flow. It was hypothesized that external forces such as overgrazing or climatic variations might potentially disturb the stability, which consequently leads to the invasion of shrubs into the grassland. The modeling results suggest that landscape linkages through the redistribution of water and soil resources across vegetation-transitions zones at the landscape scale play a significant role in the certification processes.