Small ponds are often the main source of drinking water for grazing livestock. The hydrology of these ponds must be understood so impoundments can be located, designed, and managed to avoid water shortages during dry weather. A study was conducted to measure the water balance of a stock-watering pond in the Flint Hills region of east-central Kansas from June 2005 to October 2006. The 0.35-ha pond supplied water to 250-kg yearling steers in a 65-ha pasture of native tallgrass prairie. Evaporation, depth change, and cattle consumption were measured continuously using meteorological sensors, depth recorders, and water meters. Seepage, transpiration, and inflow were measured periodically or modeled. Evaporation was also predicted from weather data using forms of the Penman and Priestley-Taylor models. Evaporation accounted for 64% of the total water loss annually, while seepage, cattle consumption, and transpiration accounted for 31%, 3%, and 2%, respectively. The greatest water loss was observed in July, with total monthly losses over 358 mm and peak daily losses sometimes exceeding 18 mm ? d 21. Cattle consumption averaged 30 L ? day 21 ? animal 21 with peak usage of 46 L ? day 21 ? animal 21. On average, the Priestley-Taylor and Penman evaporation models estimated monthly evaporation to 3% and 5%, respectively. Thus, evaporation, the main form of loss, can be predicted with simple models using data from weather station networks. Inflows from runoff proved difficult to predict and were highly dependent on antecedent soil water content. Results showed that losses from ponds can be measured or predicted with reasonable accuracy. These data could be incorporated into catchment-scale hydrology models to provide site-specific designs for stock-watering ponds and livestock-watering strategies. Resumen Los pequeñ os estanques son a menudo la principal fuente de agua potable para el ganado de pastoreo. La hidrología de estos estanques debe entenderse de manera que los embalses pueden ser ubicados, diseñ ados, manejados para evitar la escasez de agua durante la temporada seca. Se realizó un estudio para medir el balance hídrico de un estanque en la región de las colinas de Flint en la región central del este de Kansas a partir de junio del 2005 hasta octubre del 2006. El estanque de 0.35 ha suministró agua a bueyes menores de 1 añ o y 250 kg en una pradera de 65 ha pastos altos nativos. La evaporación, el cambio de profundidad, y el consumo del ganado, se midieron de forma continua utilizando sensores meteorológicos, sensores de profundidad, y de agua. La filtración, transpiración, y el flujo de agua se midieron periódicamente o se modelaron. La evaporación tambie´n se predijo de datos meteorológicos utilizando formas de los modelos de Penman y Priestley-Taylor. La evaporación representó el 64% del total de la pérdida de agua anual, mientras que la filtración, el consumo de ganado, y la transpiración representó el 31%, 3%, y 2%, respectivamente. La mayor pe´rdida de agua fue observada en Julio, con un total de las pérdidas ...

Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to measure daily values of cotton seedling ET. We designed and built plastic weighable micro-lysimeters (ML) that were 0.35 m deep with a soil volume of 6300 cm 3 . The soil core was obtained in-situ by pushing the ML well casing into the soil using a commercial soil sampler. The soil core was weighed with tension and compression type load-cells, where a change in mass of 18 g·d −1 was equivalent to a water evaporation of 1 mm·d −1 . We compared load-cell measurements of changes in mass to values measured with a portable field scale by linear regression analysis, and the slope was equal to 1, indicating no statistical difference (P = 0.05) between the two measurements. We measured and compared seedling height, root length and leaf area of cotton plants in the ML with cotton plants in the surrounding area and this comparison showed that the ML used was suitable to measure cotton seedling ET for the first 30 days after seed emergence. The root mean squared error for crop height was 0.09 cm, for leaf area index (LAI) was 0.03 m 2 ·m −2 and 6.5 cm for root length. Also, soil temperature at a 0.1 m depth was statistically (P = 0.05) the same in and outside the ML's. For two planting dates, we measured daily values of soil water evaporation (E) and cotton seedling ET. The day following an irrigation event, E was ~ 9 mm * Corresponding author. # The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual's income is derived from any public assistance program. R. J. Lascano et al. 1238d −1 and quickly declined the following days. Results showed that ML's provide an accurate tool to measure water losses from the soil and cotton plants with a LAI of ≤0.2.