Identification Of Homogeneous Zones Research Articles

Topoclimatic zoning of continental Chile

ABSTRACT In this study, the topoclimates of continental Chile are mapped. The mapping involves the identification of homogeneous zones based on the relationships between the climatic variables that characterize a location and the topography that influences the spatial behavior of these variables. The climatic and topographical zoning of the study area is conducted using a statistical methodology based on a combination of principal component analysis and cluster analysis. The climate, topography, and topoclimatic zoning yield 20, 8, and 96 clusters, respectively. Maximum topoclimatic variability is identified in sectors with mountain ranges and intermediate depression (especially in valley areas), and minimum variability is detected in the coastal sector. Furthermore, only one of the topoclimatic units has an area larger than 50,000 km2, whereas 46.8% of the units have surface areas below 2,000 km2.

Protocol for multivariate homogeneous zone delineation in precision agriculture

Uniform management of agricultural fields has been increasingly replaced with environmentally based management, which is benefited by the identification of homogeneous zones within crop fields. Such zones are based on the classification of field sites into groups of homogeneous features. Multiple causative agents of variability and the response of agricultural crops should be considered for zoning. Several correlated variables are usually measured and georeferenced for this purpose at multiple sites within the field. This paper presents an approach to promoting the integration of different statistical tools for identifying homogeneous zones based on site covariates. The methodological innovation of this work involves cleaning and re-scaling of spatial data, as well as multivariate and geostatistical analyses in a logical sequence (protocol). Statistical topics for further improvement and protocol applications are noted. The analytical process has been illustrated using a rain-fed wheat crop (60 ha) from the Argentine Pampas, with apparent electrical conductivity, elevation and soil depth as master variables for zoning, and yield, soil organic matter and clay to validate the created management zones; however, it may be applied to other production systems using georeferenced data. The R scripts and the sample file to run the proposed protocol are provided as electronic supplementary material.

Continuous streamflow simulation for index flood estimation in an Alpine basin of northern Italy

Flood frequency estimation is crucial in both engineering practice and hydrological research. Regional analysis of flood peak discharges is used for more accurate estimates of flood quantiles in ungauged or poorly gauged catchments. This is based on the identification of homogeneous zones, where the probability distribution of annual maximum peak flows is invariant, except for a scale factor represented by an index flood. The numerous applications of this method have highlighted obtaining accurate estimates of index flood as a critical step, especially in ungauged or poorly gauged sections, where direct estimation by sample mean of annual flood series (AFS) is not possible, or inaccurate. Therein indirect methods have to be used. Most indirect methods are based upon empirical relationships that link index flood to hydrological, climatological and morphological catchment characteristics, developed by means of multi-regression analysis, or simplified lumped representation of rainfall–runoff processes. The limits of these approaches are increasingly evident as the size and spatial variability of the catchment increases. In these cases, the use of a spatially-distributed, physically-based hydrological model, and time continuous simulation of discharge can improve estimation of the index flood. This work presents an application of the FEST-WB model for the reconstruction of 29 years of hourly streamflows for an Alpine snow-fed catchment in northern Italy, to be used for index flood estimation. To extend the length of the simulated discharge time series, meteorological forcings given by daily precipitation and temperature at ground automatic weather stations are disaggregated hourly, and then fed to FEST-WB. The accuracy of the method in estimating index flood depending upon length of the simulated series is discussed, and suggestions for use of the methodology provided.Editor D. Koutsoyiannis

Identification of homogeneous zones on a field based on yield of individual plots

A method is examined and an algorithm is proposed for identifying relatively homogeneous zones on a given agricultural field based on yield on its individual small plots. The initial information is formed automatically by means of harvesting machines equipped with yield sensors and global positioning system (GPS).