DOI: 10.16904/envidat.380
title: Longterm hydrological observatory Alptal (central Switzerland)

description: This data set includes 57 years of hydrometeorological measurements from small (first-order) catchments in the pre-alpine valley Alptal. Here we provide daily mean values; values in hourly or 10-min resolution can be provided on demand.
Runoff has been measured at the outlet of three small (first-order) catchments of approximately 1 km2 area: Erlenbach (two independent runoff measurements), Vogelbach and Lümpenenbach. The catchments are similar with regard to geology (Flysch) and soil conditions (clay soils), but differ in forest coverage (20 to 60%). A detailed description of the catchments can be found at https://www.wsl.ch/alptal .
Runoff in these small catchments is typically very dynamic and can temporally carry large amounts of sediment and large wood. Thus, the accuracy of the measurements at very large flow is limited. 
Meteorological variables have been measured on a meadow (Erlenhöhe) located in the Erlenbach catchment at 1220 m a.s.l. using a standard meteorological station (incl. ventilated air temperature and heated rain gauges). In addition, precipitation has also been recorded at two other locations (in the Vogelbach and Lümpenenbach catchments).
Snow measurements have been conducted weekly to monthly since 1968 at more than 15 locations (30-m transects) representing different altitudes, aspects and land uses (meadow, forest). In addition, snow depth has been recorded continuously since 2003 at Erlenhöhe, and for this location we also include a simulation of snow depth and SWE (using the numerical models COUP and DeltaSnow) that assimilates the manual weekly snow-course measurements. Details on these snow measurements can be found in Stähli, M. and Gustafsson, D. 2006. Hydrol. Proc., 20, 411-428. doi: 10.1002/hyp.6058.
Further information on the methods and sensors can be found at https://www.wsl.ch/alptal .
A first version of this data set (for the period 1968-2017) was uploaded in June 2018 at the occasion of the 50-year anniversary. This original data set was updated in February 2021 (with data from 2018 and 2019), and this data set was used for a longterm trend analysis, submitted for publication in a special issue of Hydrological Processes. Further updates of the data set (with data from 2020 to 2022) were uploaded in March 2023, February 2024, March 2025 and January 2026.
description: Resource Title: Daily meteorological and snow data (1968-2022) Alptal
 Size: 2296381 bytes
 Format: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
 URL: https://www.envidat.ch/dataset/4de5d4cd-f265-48b9-98a1-290d6f78fb23/resource/1207f33e-6efd-467f-8bf0-9e3303d529a7/download/meteorological-data_alptal_1968-2022_envidat_updated.xlsx
 Description: Air temperature, dew point temperature, relative humidity, wind speed, precipitation and global radiation have been measured (since 1981) on a meadow (Erlenhöhe) in the Erlenbach catchment. It is located at 1'220 m a.s.l. with an exposure towards west. In order to assess the spatial variability of precipiation, two additional rain gauges have been running in the Vogelbach and Lümpenenbach catchment, respectively.
For the period before 1981, meteorological variables have been extrapolated from the nearby MeteoSwiss station Einsiedeln (ca. 15 km north) to the WSL station Erlenhöhe using a linear correction factor for air temperature, wind speed and precipitation.
Snow depth has been recorded automatically since 2003. Snow water equivalent has been calculated using two numerical models: COUP model (Jansson, 2012) and DeltaSnow model (Winkler et al., 2021)

Jansson, P.-E. (2012). COUP model: model use, calibration, and validation.Transactions of the ASABE, 55(4), 1335–1344.
Winkler, M., et al. (2021): Snow water equivalents exclusively from snow depths and their temporal changes: the Δsnow model, Hydrol. Earth Syst. Sci., 25, 1165-1187, 10.5194/hess-25-1165-861 2021.
description: Resource Title: Daily runoff data from three steep torrents in the Alptal (1968-2022)
 Size: 2380268 bytes
 Format: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
 URL: https://www.envidat.ch/dataset/4de5d4cd-f265-48b9-98a1-290d6f78fb23/resource/aae85e10-27fc-48bd-9f4d-f30a65f06b17/download/runoff_daily-mean_alptal_1968-2022_envidat_updated.xlsx
 Description: Runoff, water temperature and electrical conductivity have been measured since 1968 at the outlet of three torrential catchments (with an area of approximately 1 km2 each) located in the Alptal valley: Erlenbach, Lümpenenbach and Vogelbach. This data set provides daily mean values; data at 10-min resolution can be provided on request for the period 1984-2022 (contact: alptal@wsl.ch).
description: Resource Title: Manual snow measurements Alptal (1968-2022)
 Size: 1040241 bytes
 Format: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
 URL: https://www.envidat.ch/dataset/4de5d4cd-f265-48b9-98a1-290d6f78fb23/resource/3fd1e126-25cc-490b-bb90-5fca04dc4ee9/download/snow-measurements-alptal-1969-2022_envidat_updated.xlsx
 Description: Snow depth, snow density and snow water equivalent have been measured since winter 1968/69 along more than 15 transects distributed across the Alptal valley representing different altitudes, aspects and land use (closed forest and open meadows). Length of the snow courses: 20 to 30 m. The measurement interval has been weekly to monthly.
More details about the locations and methods can be found in Stähli, M.; Gustafsson, D., (2006). Long-term investigations of the snow cover in a subalpine semi-forested catchment. Hydrological Processes, 20, 411-428. doi: 10.1002/hyp.6058.
description: Resource Title: Runoff daily mean Alptal 1968-2025 EnviDat updated
 Size: 2474639 bytes
 Format: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
 URL: https://www.envidat.ch/dataset/4de5d4cd-f265-48b9-98a1-290d6f78fb23/resource/bb1f67fd-4bd6-46fe-8b0a-e2ba2c076842/download/runoff_daily-mean_alptal_1968-2025_envidat_updated.xlsx
 Description: Runoff, water temperature and electrical conductivity have been measured since 1968 at the outlet of three torrential catchments (with an area of approximately 1 km2 each) located in the Alptal valley: Erlenbach, Lümpenenbach and Vogelbach. This data set provides daily mean values; data at 10-min resolution can be provided on request for the period 1984-2025 (contact: alptal@wsl.ch).
description: Resource Title: Meteorological data Alptal 1968-2025 EnviDat updated
 Size: 2527068 bytes
 Format: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
 URL: https://www.envidat.ch/dataset/4de5d4cd-f265-48b9-98a1-290d6f78fb23/resource/92245b92-5f2b-48a0-920d-4406cddc7d15/download/meteorological-data_alptal_1968-2025_envidat_updated.xlsx
 Description: Air temperature, dew point temperature, relative humidity, wind speed, precipitation and global radiation have been measured (since 1981) on a meadow (Erlenhöhe) in the Erlenbach catchment. It is located at 1'220 m a.s.l. with an exposure towards west. In order to assess the spatial variability of precipitation, two additional rain gauges have been running in the Vogelbach and Lümpenenbach catchment, respectively. For the period before 1981, meteorological variables have been extrapolated from the nearby MeteoSwiss station Einsiedeln (ca. 15 km north) to the WSL station Erlenhöhe using a linear correction factor for air temperature, wind speed and precipitation. Snow depth has been recorded automatically since 2003. Snow water equivalent has been calculated using two numerical models: COUP model (Jansson, 2012) and DeltaSnow model (Winkler et al., 2021)

Jansson, P.-E. (2012). COUP model: model use, calibration, and validation.Transactions of the ASABE, 55(4), 1335–1344. Winkler, M., et al. (2021): Snow water equivalents exclusively from snow depths and their temporal changes: the Δsnow model, Hydrol. Earth Syst. Sci., 25, 1165-1187, 10.5194/hess-25-1165-861 2021.
description: Resource Title: Snow measurements Alptal 1969-2025 EnviDat updated
 Size: 1059062 bytes
 Format: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
 URL: https://www.envidat.ch/dataset/4de5d4cd-f265-48b9-98a1-290d6f78fb23/resource/81eb8552-6178-4071-97f5-905416ed9972/download/snow-measurements-alptal-1969-2025_envidat_updated.xlsx
 Description: Snow depth, snow density and snow water equivalent have been measured since winter 1968/69 along more than 15 transects distributed across the Alptal valley representing different altitudes, aspects and land use (closed forest and open meadows). Length of the snow courses: 20 to 30 m. The measurement interval has been weekly to monthly. More details about the locations and methods can be found in Stähli, M.; Gustafsson, D., (2006). Long-term investigations of the snow cover in a subalpine semi-forested catchment. Hydrological Processes, 20, 411-428. doi: 10.1002/hyp.6058.