Spatial-temporal rainfall simulation using generalized linear models

We consider the problem of simulating sequences of daily rainfall at a network of sites in such a way as to reproduce a variety of properties realistically over a range of spatial scales. The properties of interest will vary between applications but typically will include some measures of "extreme'' rainfall in addition to means, variances, proportions of wet days, and autocorrelation structure. Our approach is to fit a generalized linear model (GLM) to rain gauge data and, with appropriate incorporation of intersite dependence structure, to use the GLM to generate simulated sequences. We illustrate the methodology using a data set from southern England and show that the GLM is able to reproduce many properties at spatial scales ranging from a single site to 2000 km 2 ( the limit of the available data)

The impact of grazing cattle on soil physical properties and nutrient concentrations in overland flow from pasture, Part B

This report has been prepared as part of the Environmental Research Technological Development and Innovation Programme 2000–2006. The programme is financed by the Irish Government under the National Development Plan 2000–2006.End of project reportThe loss of nutrients from agricultural land to water bodies is a serious concern in many countries. To gain information on the contribution of grazing animals to diffuse nutrient losses from pasture areas to water, this study looked at the impact of cattle on nutrient concentrations in overland flow and on soil hydrology (bulk density, macroporosity and resistance to penetration). Rainfall simulations to produce overland flow were conducted and soil physical measurements were taken on experimental plots assigned to one of two treatments: 1) cattle had unrestricted access to the plot; 2) cattle could graze the plot but they could neither walk on the plot area nor deposit excrements on it. Areas to which the cattle had free access were characterised by 57%-83% lower macroporosity, by 8%-17% higher bulk density and by 27%-50% higher resistance to penetration than areas from which the cattle were excluded. The nutrients in overland flow from grassland that were affected by the presence of grazing animals were mainly the particulate nitrogen, the organic phosphorus and the potassium concentrations. Overall, the presence of cattle had a longer lasting effect on the soil hydrological parameters measured than on the nutrient concentrations in overland flow.Environmental Protection Agenc

Evaluation of the Water Quality Impacts of Land Application of Poultry Litter

Evaluating the effect of land application of animal waste on water quality is fraught with inherent variability due to differing infiltration rates, slope, rainfall intensity and etc . Simulated rainfall technology has been used in erosion research for decades. Generally, this technology is used on plots of sufficient size (25 x 5 m) to develop rill and interrill erosion. The object of this investigation was to adapt and modify existing rainfall simulation technology used in soil erosion research for use in evaluating water quality impacts of land application of animal waste, and to test, evaluate and demonstrate it\u27s scientific validity. State of the art simulation technology was obtained from the National Soil Erosion Research Laboratory located on the campus of Purdue University. The technology was scaled (2 x 6 m) and modified to fit into field research programs having several treatments and rep 1 i cated p 1 ots . The technology was shown to meet specification needed to produce the required raindrop size and velocity, flexibility in storm intensity, while maintaining uniformity(\u3e 0.8). Equally important, the unit is portable and fits well into labor intensive runoff work requiring replication of a variety of treatments

A rainfall simulation study on the relationships between soil test P versus dissolved and potentially bioavailable particulate phosphorus forms in runoff

Runoff from clayey soils often contains abundant particulate phoshorus (PP), part of which may solubilize in surface waters. Monitoring losses of potentially bioavailable forms of PP is expensive, calling for other ways to predict them. Such predictions could be based on soil loss and available soil P indices, e.g., agronomic P status. To study correlations between P pools in runoff versus soil P saturation (by Mehlich 3 extraction; DPSM3) and acetate soil test P (PAc), 15 clayey soils of south Finland were subjected to laboratory rainfall simulation. Runoff from these simulations was analyzed for concentrations of suspended soil (TSS), dissolved molybdate-reactive P (DRP), total P (TP), and, as normalized to soil loss, potentially bioavailable forms of PP: desorbable (anion exchange resin-extractable, AER-PP/TSS) and redox-labile PP (bicarbonate- dithionite-extractable, BD-PP/TSS). Correlation coefficients (r2) between DPSM3 and DRP, AER-PP/ TSS, and BD-PP/TSS equaled 0.92, 0.77, and 0.45, respectively. Runoff P forms were also correlated to soil PAc with r2 values of 0.84, 0.56, and 0.58 for DRP, AER-PP/TSS, and BD-PP/TSS, respectively. Prediction of soil loss-normalized concentrations of potentially bioavailable PP by the agronomic PAc test was considered possible. However, such predictions have a high degree of uncertainty, evidenced by comparison to published field data. Acceptably accurate predictive equations would require a large material as a basis for their construction, and soils should probably also be grouped according to other soil properties that would account for variation in P sorption capacity

Hydrological soil behavior in areas with semi-arid vegetation (Beni Chougrane Mountains, Algeria)

Postprint (author's final draft

Monitoring soil erosion in the Souss basin, Morocco, with a multiscale object-based remote sensing approach using UAV and satellite data

This article presents a multiscale approach for detecting and monitoring soil erosion phenomena (i.e. gully erosion) in the agro-industrial area around the city of Taroudannt, Souss basin, Morocco. The study area is characterized as semi-arid with an annual average precipitation of 200 mm. Water scarcity, high population dynamics and changing land use towards huge areas of irrigation farming present numerous threats to sustainability. The agro-industry produces citrus fruits and vegetables in monocropping, mainly for the European market. Badland areas strongly affected by gully erosion border the agricultural areas as well as residential areas. To counteract the significant loss of land, land-leveling measures are attempted to create space for plantations and greenhouses. In order to develop sustainable approaches to limit gully growth the detection and monitoring of gully systems is fundamental. Specific gully sites are monitored with unmanned aerial vehicle (UAV) taking small-format aerial photographs (SFAP). This enables extremely high-resolution analysis (SFAP resolution: 2-10 cm) of the actual size of the gully channels as well as a detailed continued surveillance of their growth. Transferring the methodology on a larger scale using Quickbird satellite data (resolution: 60 cm) leads to the possibility of a large-scale analysis of the whole area around the city of Taroudannt (Area extent: ca. 350 km²). The results will then reveal possible relationships of gully growth and agro-industrial management and may even illustrate further interdependencies. The main objective is the identification of areas with high gully-erosion risk due to non-sustainable land use and the development of mitigation strategies for the study area

Bayesian approach to Spatio-temporally Consistent Simulation of Daily Monsoon Rainfall over India

Simulation of rainfall over a region for long time-sequences can be very useful for planning and policy-making, especially in India where the economy is heavily reliant on monsoon rainfall. However, such simulations should be able to preserve the known spatial and temporal characteristics of rainfall over India. General Circulation Models (GCMs) are unable to do so, and various rainfall generators designed by hydrologists using stochastic processes like Gaussian Processes are also difficult to apply over the vast and highly diverse landscape of India. In this paper, we explore a series of Bayesian models based on conditional distributions of latent variables that describe weather conditions at specific locations and over the whole country. During parameter estimation from observed data, we use spatio-temporal smoothing using Markov Random Field so that the parameters learnt are spatially and temporally coherent. Also, we use a nonparametric spatial clustering based on Chinese Restaurant Process to identify homogeneous regions, which are utilized by some of the proposed models to improve spatial correlations of the simulated rainfall. The models are able to simulate daily rainfall across India for years, and can also utilize contextual information for conditional simulation. We use two datasets of different spatial resolutions over India, and focus on the period 2000-2015. We propose a large number of metrics to study the spatio-temporal properties of the simulations by the models, and compare them with the observed data to evaluate the strengths and weaknesses of the models

Development of laboratory instrumentation for the study of soil erodibility

In order to carry out a study of the relative efficiency of various erodibility indices, and of the relative erodibility of soils developed in the Peak District of Derbyshire (England), three instruments were developed. These instruments were: a wet-sieve aggregate analyser of the Yoder pattern, a compact laboratory rainfall simulator using spray nozzles, a radiant drying unit using infra-red lamps. The efficiency of the instruments and the validity of the operating -techniques are critically evaluated and suggestions for improvement are advanced