Representative basins play an important role in the analysis of hydrological processes that are formed in natural regions, but with high potential for economic development, and frequently exposed to difficult problems caused by extreme phenomena (floods, drought). The results obtained, based on the representative basins, allow the improvement of the hydrological study, especially for regions with low density of hydrometric networks or short monitoring periods. The purpose of this study is to analyse the impact that surface soil moisture and evapotranspiration have on the runoff (during the period 2016-2021) in the upper part of the Moneasa Representative Basin (MRB), which is monitored at the Boroaia hydrometric station. MRB is located in the western part of Romania and covers an area of 14.2 km2 and has an average altitude of 680 m. The upper basin of the Moneasa River extends in the geographical region of the Apuseni Mountains, with altitudes ranging from 375 m to 981 m. The average slope of the basin, 26%, indicates a rapid runoff, and the general orientation of the slopes being south, south-east and south-west, accentuate the slope runoff processes and the melting of the snow, especially during winter and spring months. In order to analyse the impact that surface soil moisture and evapotranspiration have over the runoff in the MRB, direct measurements and satellite products (Sentinel-1 Surface Soil Moisture 1km – SSM1km, Global Evapotranspiration, working by Copernicus Global Land Service) have been used to better understand the initial condition of soil before the formation of streamflow. The analysis was carried out for the period 2016-2021. Taking 2016 like an example, results obtained for this year showed that, the streamflow for this year was characterized by an average value of 0.317 m3 s-1 and a maximum value of 3.63 m3 s-1. The annually streamflow was due to a total precipitation amount of 1411.1 mm, which made the year exceptionally rainy. Soil moisture values varied between 8.6 and 93.3% (based on SSM1km) and they characterized the study area in very wet soil moisture content (> 30%) especially in the spring months. During the summer, the impact of water evapotranspiration (> 4 mm day-1), resulted in a reduction in soil moisture content, which could drop to moderate or very dry conditions (< 20%). Soil moisture and streamflow respond differently from one season to another. For example, precipitation of 40-50 mm/day ensures soil moisture greater than 90% in January and February, while in September and October the same amount of precipitation result in a soil moisture of less than 50%. Results showed that the impact of soil moisture is observed especially in the base flow during the period of high level of river (e.q. from January 29th to March 25th), where base flow values are maximized and range between 0.19 - 0.59 m3 s-1, accounting for more than 50% of streamflow. Due to its characteristics, regarding the underground water conditions that ensure a homogeneity of the dynamics in the phreatic zone, and with a great diversity of factors influencing the flow (relief, soil, vegetation and climate), results obtained for Moneasa Representative Basin (MRB) can ensure an overview of runoff characteristics, from other neighbour basins.
The influence of soil moisture and evapotranspiration on runoff in small catchments
Ortenzi, Sofia;Di Matteo, Lucio;
2024
Abstract
Representative basins play an important role in the analysis of hydrological processes that are formed in natural regions, but with high potential for economic development, and frequently exposed to difficult problems caused by extreme phenomena (floods, drought). The results obtained, based on the representative basins, allow the improvement of the hydrological study, especially for regions with low density of hydrometric networks or short monitoring periods. The purpose of this study is to analyse the impact that surface soil moisture and evapotranspiration have on the runoff (during the period 2016-2021) in the upper part of the Moneasa Representative Basin (MRB), which is monitored at the Boroaia hydrometric station. MRB is located in the western part of Romania and covers an area of 14.2 km2 and has an average altitude of 680 m. The upper basin of the Moneasa River extends in the geographical region of the Apuseni Mountains, with altitudes ranging from 375 m to 981 m. The average slope of the basin, 26%, indicates a rapid runoff, and the general orientation of the slopes being south, south-east and south-west, accentuate the slope runoff processes and the melting of the snow, especially during winter and spring months. In order to analyse the impact that surface soil moisture and evapotranspiration have over the runoff in the MRB, direct measurements and satellite products (Sentinel-1 Surface Soil Moisture 1km – SSM1km, Global Evapotranspiration, working by Copernicus Global Land Service) have been used to better understand the initial condition of soil before the formation of streamflow. The analysis was carried out for the period 2016-2021. Taking 2016 like an example, results obtained for this year showed that, the streamflow for this year was characterized by an average value of 0.317 m3 s-1 and a maximum value of 3.63 m3 s-1. The annually streamflow was due to a total precipitation amount of 1411.1 mm, which made the year exceptionally rainy. Soil moisture values varied between 8.6 and 93.3% (based on SSM1km) and they characterized the study area in very wet soil moisture content (> 30%) especially in the spring months. During the summer, the impact of water evapotranspiration (> 4 mm day-1), resulted in a reduction in soil moisture content, which could drop to moderate or very dry conditions (< 20%). Soil moisture and streamflow respond differently from one season to another. For example, precipitation of 40-50 mm/day ensures soil moisture greater than 90% in January and February, while in September and October the same amount of precipitation result in a soil moisture of less than 50%. Results showed that the impact of soil moisture is observed especially in the base flow during the period of high level of river (e.q. from January 29th to March 25th), where base flow values are maximized and range between 0.19 - 0.59 m3 s-1, accounting for more than 50% of streamflow. Due to its characteristics, regarding the underground water conditions that ensure a homogeneity of the dynamics in the phreatic zone, and with a great diversity of factors influencing the flow (relief, soil, vegetation and climate), results obtained for Moneasa Representative Basin (MRB) can ensure an overview of runoff characteristics, from other neighbour basins.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
