In the Erlenbach stream, a pre‐alpine steep channel in Switzerland, sediment transport has been monitored for more than 25 years. Near the confluence with the main valley river, stream flow is monitored and sediment is collected in a retention basin with a capacity of about 2000 m3. The basin is surveyed at regular intervals and after large flood events. In addition, sediment transport has been continuously monitored with piezoelectric bedload impact and geophone sensors since 1986. In 2008–2009, the measuring system in the Erlenbach stream was enhanced by installing an automatic system to obtain bedload samples. Movable metal baskets are mounted on a rail at the downstream wall of the large check dam above the retention basin, and they can be moved automatically into the flow to take bedload transport samples. The wire mesh of the baskets has a spacing of 10 mm to sample all sediment particles coarser than this size (which is about the limiting grain size detected by the geophones). The upgraded measuring system permits to obtain bedload samples over short sampling periods and to measure the grain size distribution of the transported material and its variation over time and with discharge. The analysis of calibration relationships for the geophone measuring system confirms findings from very similar measurements which were performed until 1999 with piezoelectric bedload impact sensors; there is a linear relationship between impulse counts and bedload mass passing over the sensors. Findings from flume experiments are used to discuss the most important factors which affect the calibration of the geophone signal. The bedload transport rates as measured by the moving baskets are among the highest measured in natural streams, with values of the order of several kilograms per meter per second. Copyright © 2012 John Wiley & Sons, Ltd.

Long-term data on precipitation and runoff are essential to draw firm conclusions about the behavior and trends of hydrological catchments that may be influenced by land use and climate change. Here the longest continuous runoff records from small catchments (<1 km(2)) in Switzerland (and possibly worldwide) are reported. The history of the hydrological monitoring in the Sperbel- and Rappengraben (Emmental) is summarized, and inherent uncertainties in the data arising from the operation of the gauges are described. The runoff stations operated safely for more than 90% of the summer months when most of the major flood events occurred. Nevertheless, the absolute values of peak runoff during the largest flood events are subject to considerable uncertainty. The observed differences in average, base, and peak runoff can only partly be attributed to the substantial differences in forest coverage. This treasure trove of data can be used in various ways, exemplified here with an analysis of the generalized extreme value distributions of the two catchments. These distributions, and hence flood return periods, have varied greatly in the course of one century, influenced by the occurrence of single extreme events. The data will be made publicly available for the further analysis of the mechanisms governing the runoff behavior of small catchments, as well as for testing stochastic and deterministic models.

Equations for estimating the 7-day 2-year and 7-day 10-year low flow at sites on ungaged streams are presented. Regression analysis was used to develop equations relating basin characteristics and low-flow characteristics at 58 continuous-record gaging stations and 151 partial-record sites. Significant basin characteristics in the equations are drainage area and percentage of drainage basin underlain by permeable bedrock units. The study area, which encompasses the western two-thirds of the State, is divided into three regions based on the similarity of basin characteristics within each region. The analysis includes records for only those stations that are not highly regulated and have drainage areas less than 1,000 square miles.A three-step method is used to estimate low-flow characteristics at ungaged sites. The first step involves the use of a logistic regression to determine the probability that the 7-day annual minimum flow is zero at the site of interest. The second step uses this estimated probability of 7-day annual zero flow to determine if the estimated value of the 7day 2-year or the 7-day 10-year low flow is zero or needs to be estimated from one of the regional equations, which are based on a generalized-least-squares model for sites with non-zero flow. The third step involves the use of the regional equation, if flow is indicated, to determine the 7-day 2-year and 10-year low-flow values.Computer software has been written to facilitate the computation of low-flow characteristics at sites of interest The software is provided in written form and on a disk. «(*) «(*) =-^-rŵ here *W = P

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