Manuscrito recibido el 17 de junio de 2017, en versión final 10 de diciembre de 2017) Para citar este documento Cazenave, H.W.,. (2017). Casa de Piedra: efectos de las aguas claras en la hidrografía del río Colorado. Boletín geográfico, 39, 109-125. ResumenLa construcción del dique de embalse Casa de Piedra en el tramo final del alto valle del río Colorado, modificó radicalmente las condiciones hidrológicas del curso aguas abajo de la represa. Esas modificaciones se advierten muy especialmente en el trasporte de sedimento en suspensión, de los que el río Colorado es un agente sumamente activo y que ha generado su nombre. Con la construcción del dique, al perder las aguas capacidad de trasporte al llegar al lago, precipitan hacia el fondo del mismo. Consecuentemente las aguas que eroga la represa, al carecer de carga sólida tienen una notable capacidad erosiva que acelera los procesos hidrográficos de aguas abajo incrementando la meandrosidad del curso y el proceso de formación de esas curvas; también cambia la salinidad del agua. Esos caudales son las llamadas -aguas claras‖ y su poder erosivo tiene a menudo efectos negativos en las áreas bajo riego.A los efectos de cuantificar la citada aceleración en la formación de curvas se tomó un tramo con cartografía fiable que refleja un período de aproximadamente 25 años previos y posteriores a la construcción de la represa, comparándose en cada uno la aparición y desaparición de meandros. La variación fue significativa considerando los relativamente breves tiempos. Ello se vio refrendado con un nuevo vuelo aerofotográfico que demostró el incremento de la cantidad de meandros en el corto lapso sobre el tramo en consideración Palabras clave: Río Colorado, Represa, Sedimentos, Erosión, Meandros 1 Fundación Chadileuvú. Universidad Nacional de La Pampa (retirado). Santiago Marzo norte 271. Santa Rosa. La Pampa.

Factors descriptive of a drainage‐basin as related to its hydrology may be classified broadly as: (1) Morphologic—These factors depend only on the topography of the land forms of which the drainage‐basin is composed and on the form and extent of the stream‐system or drainage‐net within it. ((2) Soil factors—This group includes factors descriptive of the materials forming the groundwork of the drainage‐basin, including all those physical properties involved in the moisture‐relations of soils. (3) Geologic‐structural factors—These factors relate to the depths and characteristics of the underlying rocks and the nature of the geologic structures in so far as they are related to ground‐water conditions or otherwise to the hydrology of the drainage‐basin. (4) Vegetational factors—These are factors which depend wholly or in part on the vegetation, natural or cultivated, growing within the drainage‐basin. (5) Climatic‐hydrologic factors—Climatic factors include: Temperature, humidity, rainfall, and evaporation, but as humidity, rainfall, and evaporation may also be considered as hydrologic, the two groups of factors have been combined. Hydrologic factors relate specially to conditions dependent on the operation of the hydrologic cycle, particularly with reference to runoff and ground‐water.

For some years the author has used the term “infiltration” to describe the process involved where water soaks into or is absorbed by the soil. Absorption, imbibition, and percolation are often used in much the same sense. It seems better to confine the use of “percolation” to the free downward flow by gravity of water in the zone of aeration—a process for which a distinctive term is needed. “Absorption” includes the entrance of air as well as water, both liquid and vapor, into the soil (see Patten and Gallagher, Absorption of vapors and gases by soils, U.S. Dep. Agric., Bul. 51, Bur. Soils, Wash., 1908; also Charles H. Lee, On absorption and transpiration, Trans. Amer. Geophys. Union, 1932, pp. 288–298). “Infiltration” is limited to water in the liquid form and is more accurately descriptive of the physical processes by which rain enters the soil. “Water‐penetration” is also sometimes used as if synonymous with infiltration. Its use should be restricted to the depth below soil‐surface reached by the given surface infiltration.

Biochar, a co-product of thermochemical conversion of lignocellulosic materials into advanced biofuels, may be used as a soil amendment to enhance the sustainability of biomass harvesting. We investigated the impact of biochar amendments (0, 5, 10, and 20 g-biochar kg− 1 soil) on the quality of a Clarion soil (Mesic Typic Hapludolls), collected (0-15 cm) in Boone County, Iowa. Repacked soil columns were incubated for 500 days at 25 °C and 80% relative humidity. On week 12, 5 g of dried and ground swine manure was incorporated into the upper 3 cm of soil for half of the columns. Once each week, all columns were leached with 200 mL of 0.001 M CaCl2. Soil bulk density increased with time for all columns and was significantly lower for biochar amended soils relative to the un-amended soils. The biochar amended soils retained more water at gravity drained equilibrium (up to 15%), had greater water retention at − 1 and −5 bars soil water matric potential, (13 and 10% greater, respectively), larger specific surface areas (up to 18%), higher cation exchange capacities (up to 20%), and pH values (up to 1 pH unit) relative to the un-amended controls. No effect of biochar on saturated hydraulic conductivity was detected. The biochar amendments significantly increased total N (up to 7%), organic C (up to 69%), and Mehlich III extractable P, K, Mg and Ca but had no effect on Mehlich III extractable S, Cu, and Zn. The results indicate that biochar amendments have the potential to substantially improve the quality and fertility status of Midwestern agricultural soils. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. Biochar, a co-product of thermochemical conversion of lignocellulosic materials into advanced biofuels, may be used as a soil amendment to enhance the sustainability of biomass harvesting. We investigated the impact of biochar amendments (0, 5, 10, and 20 g-biochar kg − 1 soil) on the quality of a Clarion soil (Mesic Typic Hapludolls), collected (0-15 cm) in Boone County, Iowa. Repacked soil columns were incubated for 500 days at 25°C and 80% relative humidity. On week 12, 5 g of dried and ground swine manure was incorporated into the upper 3 cm of soil for half of the columns. Once each week, all columns were leached with 200 mL of 0.001 M CaCl 2 . Soil bulk density increased with time for all columns and was significantly lower for biochar amended soils relative to the un-amended soils. The biochar amended soils retained more water at gravity drained equilibrium (up to 15%), had greater water retention at − 1 and −5 bars soil water matric potential, (13 and 10% greater, respectively), larger specific surface areas (up to 18%), higher cation exchange capacities (up to 20%), and pH values (up to 1 pH unit) relative to the un-amended controls. No effect of biochar on saturated hydraulic conductivity was detected. The biochar amendments significantly increased total N (up to 7%), orga...

Application of biochar to highly weathered tropical soils has been shown to enhance soil quality and decrease leaching of nutrients. Little, however, is known about the effects of biochar applications on temperate region soils. Our objective was to quantify the impact of biochar on leaching of plant nutrients following application of swine manure to a typical Midwestern agricultural soil. Repacked soil columns containing 0, 5, 10, and 20 g-biochar kg− 1-soil, with and without 5 g kg− 1 of dried swine manure were leached weekly for 45 weeks. Measurements showed a significant decrease in the total amount of N, P, Mg, and Si that leached from the manure-amended columns as biochar rates increased, even though the biochar itself added substantial amounts of these nutrients to the columns. Among columns receiving manure, the 20 g kg− 1 biochar treatments reduced total N and total dissolved P leaching by 11% and 69%, respectively. By-pass flow, indicated by spikes in nutrient leaching, occurred during the first leaching event after manure application for 3 of 6 columns receiving manure with no biochar, but was not observed for any of the biochar amended columns. These laboratory results indicate that addition of biochar to a typical Midwestern agricultural soil substantially reduced nutrient leaching, and suggest that soil-biochar additions could be an effective management option for reducing nutrient leaching in production agriculture. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. Application of biochar to highly weathered tropical soils has been shown to enhance soil quality and decrease leaching of nutrients. Little, however, is known about the effects of biochar applications on temperate region soils. Our objective was to quantify the impact of biochar on leaching of plant nutrients following application of swine manure to a typical Midwestern agricultural soil. Repacked soil columns containing 0, 5, 10, and 20 g-biochar kg − 1 -soil, with and without 5 g kg − 1 of dried swine manure were leached weekly for 45 weeks. Measurements showed a significant decrease in the total amount of N, P, Mg, and Si that leached from the manure-amended columns as biochar rates increased, even though the biochar itself added substantial amounts of these nutrients to the columns. Among columns receiving manure, the 20 g kgbiochar treatments reduced total N and total dissolved P leaching by 11% and 69%, respectively. By-pass flow, indicated by spikes in nutrient leaching, occurred during the first leaching event after manure application for 3 of 6 columns receiving manure with no biochar, but was not observed for any of the biochar amended columns. These laboratory results indicate that addition of biochar to a typical Midwestern agricultural soil substantially reduced nutrient leaching, and suggest that soil-biochar additions could be an effective management option for reducing nutrient leaching in ...

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The thermal conductivity and water content relationship is required for quantitative study of heat and water transfer processes in saturated and unsaturated soils. In this study, we developed an improved model that describes the relationship between thermal conductivity and volumetric water content of soils. With our new model, soil thermal conductivity can be estimated using soil bulk density, sand (or quartz) fraction, and water content. The new model was first calibrated using measured thermal conductivity from eight soils. As a first step in validation, predicted thermal conductivity with the calibrated model was compared with measured thermal conductivity on four additional soils. Except for the sand, the root mean square error (RMSE) of the new model ranged from 0.040 to 0.079 W m−1 K−1, considerably less than that of the Johansen model (0.073–0.203 W m−1 K−1) or the Côté and Konrad model (0.100–0.174 W m−1 K−1). A second validation test was performed by comparing the three models with literature data that were mostly used by Johansen and Côté and Konrad to establish their models. The RMSEs of the new model, the Johansen model, and the Côté and Konrad model were 0.176, 0.176, and 0.177 W m−1 K−1, respectively. The results show that the new model provided accurate approximations of soil thermal conductivity for a wide range of soils. All of the models tested demonstrated sensitivity to the quartz fraction of coarse‐textured soils.

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