Land use and climate are two determinant factors of water yield within a watershed. Understanding the effects of these two variables is key for the decision-making process within watersheds. Hydrologic modeling can be used for this purpose and the integration of future climate scenarios to calibrated models widens the spectrum of analysis. Such types of studies have been carried out in many areas of the world, including the Amazon Basin of South America. However, there is a lack of understanding on the effect of land use/land cover and climate change on Andean watersheds of this continent. Our study focused on the evaluation of water yield under different land use and climate scenarios using the semi-distributed hydrological model known as the Soil and Water Assessment Tool (SWAT) model. We worked on the Tona watershed (Colombia, South America), the most important source of water for a metropolitan population. Our results compared water yield estimates for historical conditions (1987–2002) with those of future combined scenarios for land use and climate for the 2006–2050 period. The modeling effort produced global estimates of water yield (average annual values) and, at the subwatershed level, identified strategic areas on which the protection and conservation activities of water managers can be focused.

A solution to the problem of transient one-dimensional heat conduction in a finite domain is developed through the use of parametric fractional derivatives. The heat diffusion equation is rewritten as anomalous diffusion, and both analytical and numerical solutions for the evolution of the dimensionless temperature profile are obtained. For large slab thicknesses, the results using fractional order derivatives match the semi-infinite domain solution for Fourier numbers, Fo∊[0,1/16]. For thinner slabs, the fractional order solution matches the results obtained using the integral transform method and Green’s function solution for finite domains. A correlation is obtained to display the variation of the fractional order p as a function of dimensionless time (Fo) and slab thickness (ζ) at the boundary ζ=0.

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With the rising costs of electricity due to increasing demand of electric power, liquid desiccant systems have received significant attention as a way to reduce latent loads on air conditioning systems. In particular, the performance of liquid desiccant systems in humid climates has shown significant reductions in energy consumption. In general, these liquid desiccant systems are composed by an absorber or dehumidifier and a regenerator that utilizes a heat source to reject the water from the diluted liquid desiccant. As the humidity of the air is absorbed at the dehumidifier, the temperature of the liquid desiccant increases due to the addition of heat from the enthalpy of condensation of the water vapor. Thus, many designs of liquid desiccant absorbers include the flow of a cooling fluid that removes heat from the liquid desiccant. A novel application of liquid desiccant systems corresponds to the localized removal of moisture from the air inside low temperature rooms that contain relatively high levels of humidity such as refrigerated warehouses for the food industry. The purpose is to reduce the formation of ice at the surface of the evaporator. Due to the low temperature of the air inside these rooms, no cooling fluid is necessary for the removal of heat from the liquid desiccant. Thus, the designs of the absorbers differ from the designs used for ambient air temperatures. In this paper, a mathematical model of the heat and mass transfer for an adiabatic parallel-plate absorber for which a thin film of liquid desiccant flows down its walls and dehumidifies the air in cross-flow configuration is developed.

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