Daily Archives: February 19, 2013

Evapotranspiration (ET) rates mapped for the United States

Sanford, Ward E. and David L. Selnick, 2012. Estimation of Evapotranspiration Across the Conterminous United States Using a Regression with Climate and Land-Cover Data. Journal of the American Water Resources Association (JAWRA) 49(1): 217-230. DOI: 10.1111 ⁄ jawr.12010


Evapotranspiration (ET) is an important quantity for water resource managers to know because it often represents the largest sink for precipitation (P) arriving at the land surface. In order to estimate actual ET across the conterminous United States (U.S.) in this study, a water-balance method was combined with a climate and land-cover regression equation. Precipitation and streamflow records were compiled for 838 watersheds for 1971-2000 across the U.S. to obtain long-term estimates of actual ET. A regression equation was developed that related the ratio ET⁄P to climate and land-cover variables within those watersheds. Precipitation and temperatures were used from the PRISM climate dataset, and land-cover data were used from the USGS National Land Cover Dataset. Results indicate that ET can be predicted relatively well at a watershed or county scale with readily available climate variables alone, and that land-cover data can also improve those predictions. Using the climate and land-cover data at an 800-m scale and then averaging to the county scale, maps were produced showing estimates of ET and ET⁄P for the entire conterminous U.S. Using the regression equation, such maps could also be made for more detailed state coverages, or for other areas of the world where climate and land-cover data are plentiful.

Click here for full article (Open Source).

Nervous system function impaired….by chronic fluorosis

Adali MK, Varol E, Aksoy F, Icli A, Ersoy IH, Ozaydin M, Erdogan D, Dogan A. Impaired Heart Rate Recovery in Patients with Endemic Fluorosis. Biol Trace Elem Res. 2013 Feb 16.

The objective of the present study was to determine the heart rate recovery index (HRRI), a marker of autonomic nervous system function in patients with endemic fluorosis. Forty patients with endemic fluorosis (16 men/24 women) and 40 age-, sex-, and body mass index-matched healthy controls (16 men/24 women) with normal fluoride intake were enrolled in this study. HRRI was calculated by subtracting the heart rate values at the first, second, and third minutes of the recovery phase from the peak heart rate (HRRI 1, HRRI 2, HRRI 3). Urine fluoride levels of fluorosis patients were significantly (P < 0.001) higher than control subjects as expected. HRRI 2 was significantly lower in fluorosis patients than in the controls. The incidence of abnormal HRRI 1 was significantly higher in fluorosis patients than in the controls (P < 0.05). We observed that HRRI, a marker of autonomic nervous system function, is impaired in patients with chronic fluorosis.

Click here for full text (fee).