Systematic parameter fitting for conceptual models of catchment hydrology

Imperial Users onl

Heterogeneity in catchment properties: a case study of Grey and Buller catchments, New Zealand

International audienceThe scaling behaviour of landscape properties, including both morphological and landscape patchiness, is examined using monofractal and multifractal analysis. The study is confined to two neighbouring meso-scale catchments on the west coast of the South Island of New Zealand. The catchments offer a diverse but largely undisturbed landscape with population and development impacts being extremely low. Bulk landscape properties of the catchments (and their sub-basins) are examined and show that scaling of stream networks follow Hack's empirical rule, with exponents ?0.6. It is also found that the longitudinal and transverse scaling exponents of stream networks equate to ?l ?0.6 and ?w? 0.4, indicative of self-affine scaling. Catchment shapes also show self-affine behaviour. Further, scaling of landscape patches show multifractal behaviour and the analysis of these variables yields the characteristic parabolic curves known as multifractal spectra. A novel analytical approach is adopted by using catchments as hydrological cells at various sizes, ranging from first to sixth order, as the unit of measure. This approach is presented as an alternative to the box-counting method as it may be much more representative of hydro-ecological processes at catchment scales. Multifractal spectra are generated for each landscape property and spectral parameters such as the range in ? (Holder exponent) values and maximum dimension at ?0, (also known as the capacity dimension Dcap), are obtained. Other fractal dimensions (information Dinf and correlation Dcor) are also calculated and compared. The dimensions are connected by the inequality Dcap?Dinf?Dcor. Such a relationship strongly suggests that the landscape patches are heterogeneous in nature and that their scaling behaviour can be described as multifractal. The quantitative parameters obtained from the spectra may provide the basis for improved parameterisation of ecological and hydrological models. Keywords: fractal, multifractal, scaling, landscape, patchines

Heterogeneity in catchment properties: a case study of Grey and Buller catchments, New Zealand

The scaling behaviour of landscape properties, including both morphological and landscape patchiness, is examined using monofractal and multifractal analysis. The study is confined to two neighbouring meso-scale catchments on the west coast of the South Island of New Zealand. The catchments offer a diverse but largely undisturbed landscape with population and development impacts being extremely low. Bulk landscape properties of the catchments (and their sub-basins) are examined and show that scaling of stream networks follow Hack’s empirical rule, with exponents ∼0.6. It is also found that the longitudinal and transverse scaling exponents of stream networks equate to νl ≈0.6 and νw≈ 0.4, indicative of self-affine scaling. Catchment shapes also show self-affine behaviour. Further, scaling of landscape patches show multifractal behaviour and the analysis of these variables yields the characteristic parabolic curves known as multifractal spectra. A novel analytical approach is adopted by using catchments as hydrological cells at various sizes, ranging from first to sixth order, as the unit of measure. This approach is presented as an alternative to the box-counting method as it may be much more representative of hydro-ecological processes at catchment scales. Multifractal spectra are generated for each landscape property and spectral parameters such as the range in α (Holder exponent) values and maximum dimension at α0, (also known as the capacity dimension Dcap), are obtained. Other fractal dimensions (information Dinf and correlation Dcor) are also calculated and compared. The dimensions are connected by the inequality Dcap≥Dinf≥Dcor. Such a relationship strongly suggests that the landscape patches are heterogeneous in nature and that their scaling behaviour can be described as multifractal. The quantitative parameters obtained from the spectra may provide the basis for improved parameterisation of ecological and hydrological models. Keywords: fractal, multifractal, scaling, landscape, patchines

Distributed Hydrologic Modeling using GIS and Topmodel

This paper describes a distributed modeling approach applied to modeling stream flow in the 3817 km2 Grey River in New Zealand. We have assembled and used a modeling system centered on TOPMODEL, for the simulation of saturation excess runoff based upon topography, but included other components to represent all the hydrologic processes deemed relevant. Precipitation was spatially interpolated from twenty five rain gauges using linear interpolation on Delauney triangles and scaling by an annual rainfall surface to represent orographic effects. The model included components for estimating reference evapotranspiration from temperature, modeling interception and throughfall, an unsaturated zone soil layer that delayed water inputs to the saturated zone and provided infiltration excess runoff generation capability, and a kinematic wave channel routing component. Procedures were developed to generate model input files from digital elevation model and land resource inventory Geographic Information System (GIS) data. Model elements are subwatersheds automatically extracted based upon the channel network extracted from the digital elevation model and a specified stream order threshold. Model element parameters are linked to GIS information averaged over each subwatershed. We were able to handle subdivision into up to 200 subwatersheds. The model was calibrated using an interactive calibration package utilizing the Gauss-Marquardt method. The calibration uses scale multipliers to retain GIS landcover derived relative differences between parameters across subwatersheds. Model parameters were first calibrated against a small subwatershed for one year then independently tested there for a later year. The calibration used precipitation measured at this small watershed while the validation exercised the precipitation interpolation methodology. The model was then applied to the whole Grey basin, with the same parameters and compared to flow measured at the basin outlet, and eight other water level recorders in the basin. Our results indicate that streamflow estimates are sensitive to uncertainty in the precipitation due to variability and orographic effects and that this precipitation uncertainty dominates over uncertainty in other basin characteristics. We discuss efforts to reconcile the spatial pattern of rainfall with rain gage and stream flow measurements across this watershed

Overexpression of TFAP2C in invasive breast cancer correlates with a poorer response to anti-hormone therapy and reduced patient survival

The AP-2gamma transcription factor encoded by the TFAP2C gene is a member of a family of homologous DNA binding proteins that play essential roles during vertebrate embryogenesis but show a restricted pattern of expression in the adult. Elevated expression of the AP-2alpha and AP-2gamma family members has been associated with a number of neoplasms, particularly breast cancer. Here we present an exploratory immunohistochemical study of an archival primary breast tumour series (n = 75) with parallel clinicopathological data using a new, well-characterized antibody to AP-2gamma. Heterogeneous, exclusively nuclear expression of AP-2gamma was found in the epithelial and myoepithelial compartments of normal breast and within tumour epithelial cells. In the breast cancer series, the most notable association was a correlation between elevated levels of AP-2gamma and shortened patient survival (p = 0.0009*). This relationship was also conserved in ER-positive and ErbB2-negative patients; sub-groups generally considered to have a relatively good prognosis. When patient data for survival and duration of treatment response on anti-hormone therapy were examined by multivariate analysis, AP-2gamma was revealed in this study to be an independent predictor of outcome for both survival (p = 0.005) and response to anti-hormone therapy (p = 0.046). Studies using in vitro models confirmed that while tamoxifen response is associated with lower levels of AP-2gamma, acquisition of resistance to this and other anti-hormone measures (eg faslodex or oestrogen deprivation) is associated with high levels of nuclear AP-2gamma. Together these data suggest that elevated tumour AP-2gamma expression can contribute to the failure of cells to growth arrest following anti-hormone treatment and lead to sustained growth and poorer patient outcome