Abstract:Eective control of nonpoint source pollution from contaminants transported by runo requires information about the source areas of surface runo. Variable source hydrology is widely recognized by hydrologists, yet few methods exist for identifying the saturated areas that generate most runo in humid regions. The Soil Moisture Routing model is a daily water balance model that simulates the hydrology for watersheds with shallow sloping soils. The model combines elevation, soil, and land use data within the geographic information system GRASS, and predicts the spatial distribution of soil moisture, evapotranspiration, saturation-excess overland¯ow (i.e., surface runo), and inter¯ow throughout a watershed. The model was applied to a 170 hectare watershed in the Catskills region of New York State and observed stream¯ow hydrographs and soil moisture measurements were compared to model predictions. Stream¯ow prediction during non-winter periods generally agreed with measured¯ow resulting in an average r 2 of 0 . 73, a standard error of 0 . 01 m 3 /s, and an average Nash-Sutclie eciency R 2 of 0 . 62. Soil moisture predictions showed trends similar to observations with errors on the order of the standard error of measurements. The model results were most accurate for non-winter conditions. The model is currently used for making management decisions for reducing non-point source pollution from manure spread ®elds in the Catskill watersheds which supply New York City's drinking water.

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Novel joint delay Doppler probability density functions for vehicle-to-vehicle communications channels are introduced. Prior measurements of vehicle-to-vehicle channels have unveiled their nonstationarity; thus, the wide-sense stationary and also the uncorrelated scattering assumption for such channels is often violated, which makes their modeling challenging. In this work it is proposed to exploit geometry-based stochastic modeling to cope with the nonstationarity of vehicle-to-vehicle channels. To this end, delay-dependent Doppler pdfs are derived for arbitrary times. It is assumed that scatterers are randomly distributed on an ellipse with two moving vehicles being in its foci. The proposed approach allows reducing the dimensionality of the resulting problem. This in turn leads to a significantly simplified derivation of the delay-dependent Doppler pdfs for general vehicle-to-vehicle propagation environments; moreover, the resulting computations can be performed almost fully analytically. By combining the calculated Doppler pdf with a delay pdf, the joint pdf of delay and Doppler is obtained. The joint pdf then can be put into relation with the generalized local scattering function. The presented modeling approach is simple yet very scalable and accurate, which allows its application in different vehicular scenarios. The obtained modeling results correspond very well with measurement data reported in prior works.Index Terms-Geometric-stochastic channel modeling, nonstationary modeling, scatter channel, vehicle-to-vehicle channel, wideband channel model.

This study was a statistical evaluation of the prevalence of infiltration excess runoff ͑i.e., Hortonian flow͒ for undeveloped areas within New York City ͑NYC͒ watersheds. Identifying the hydrological processes generating runoff is central to developing watershed management strategies for protecting water quality. Fifteen-minute rainfall data from East Sidney, N.Y. ͑1971-2002͒ were used as maximum observed intensities. Maximum exceedance analyses were performed on a monthly basis to investigate seasonal rainfall intensity trends. Hortonian flow was assumed to occur whenever the rainfall intensity exceeded the soil permeability. Soil permeabilities were obtained from the U.S. Natural Resource Conservation Service soil survey. Results show that Hortonian flow is unlikely to occur anywhere for events smaller than the 3-year 15-min event. Only for the summer months, May-August, is Hortonian flow expected for 15-min intensities of Ͻ10-year magnitude. However, the summer results are overpredicted by this analysis because these months typically have the driest soil conditions and thus the highest infiltration capacity. This analysis concludes that infiltration excess runoff is not a dominant runoff process in undeveloped portions of NYC watersheds.

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When tropical forests are felled, subsequent land uses affect surface runoff, soil erosion, and soil compaction. In some cases, they can markedly change the hydrology of a region with disastrous effects on human life. The objective of this paper is to investigate the effect of rainfall on stream hydrology due to conversion of primary forests to agriculture. Near surface water dynamics were compared for three land uses on the steep hillsides in the Talgua River Watershed in Honduras: degraded grasscovered field; traditional coffee plantation; and primary forest. Infiltration and surface runoff rates were measured using several methods. A clear difference was observed in hydraulic conductivity between the degraded and non-degraded lands. The degraded grass-covered hillslopes developed a surface restrictive layer with a low saturated hydraulic conductivity of 8 to 11 mm/hr, resulting in more frequent overland flow than traditional coffee plantation and primary forest. Soils under the latter two land-use types maintained high infiltration capacities and readily conducted water vertically at rates of 109 and 840 mm/hr, respectively. Dye tests confirmed that the coffee plantation and primary forest both maintained well-connected macropores through which water flowed readily. In contrast, macropores in the degraded soil profile were filled by fine soil particles. Soils in the degraded grass-covered field also showed more compaction than soils in the coffee plantation.

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