Defining minimum runoff length allows for discriminating biocrusts and rainfall events Lázaro, Roberto López Canfín, Clément Semiarid Biological soil crust Runoff connectivity Length slope factor Infiltration Taberans Desert This study was started in the context of the research projects PECOS (REN2003-04570/GLO) and PREVEA (CGL2007-63258/BOS) , both funded by the Spanish National Plan for RD&I and by the European ERDF Funds (European Regional Development Fund) , and continued during the project SCIN (Soil Crust In-terNational, PRI-PIMBDV-2011-0874, European project of ERA-NET BIODIVERSA, the Spanish team being funded by the Spanish Ministry of Economy and Competitiveness) . The work was finally supported and culminated by the DINCOS project (CGL2016-78075-P, Spanish State Programme for Scientific Research) and by the European ERDF Funds (Euro-pean Regional Development Fund) . Consuelo Rubio's partici-pation was possible thanks to the contract as a doctoral student FPU18/00035. Dr. Javier Barbero advised us on mathemati-cal issues. Special thanks: This research was kindly facilitated by the Viciana brothers, landowners of the El Cautivo field site. The runoff coefficient (RC) is widely used despite requiring to know the effective contributing area, which cannot be known a priori. In a previous work, we defined runoff length (RL), which is difficult to measure. This work aimed to define the minimum RL (mRL), a quantitative and easy proxy of RL, for use in a pilot study on biocrusts in the Tabernas Desert, Spain. We show that RC decreases according to a hyperbola when the contributing area increases, the independent variable being the length of the effective contributing area and its coefficient involving the effects of rainfall and surface features and antecedent conditions. We defined the mRL as the length of the effective contributing area making RC = 1, which is calculated regardless of the area. We studied mRL from three biocrust types and 1411 events clustered in seven categories. The mRL increased with rain volume and intensity, catchment area and slope, whereas plant cover and biocrust succession (with one exception) had a negative effect. Depending on the plot, mRL reached up 3.3–4.0 m on cyanobacterial biocrust, 2.2–7.5 m on the most widespread lichens, and 1.0–1.5 m on late-successional lichens. We discuss the relationships of mRL with other runoff-related parameters. 2021-12-17T12:19:59Z 2021-12-17T12:19:59Z 2021-11-15 journal article Lázaro, R... [et al.] (2021). Defining minimum runoff length allows for discriminating biocrusts and rainfall events. Journal of Hydrology and Hydromechanics, 69(4) 387-399. [https://doi.org/10.2478/johh-2021-0029] http://hdl.handle.net/10481/72111 10.2478/johh-2021-0029 eng http://creativecommons.org/licenses/by-nc-nd/3.0/es/ open access Atribución-NoComercial-SinDerivadas 3.0 España Sciendo