Effects of flow regime alteration on fluvial habitats and riparian quality in a semiarid Mediterranean basin

Abstract

1The Segura River Basin is one of the most arid and regulated zones in the 2 Mediterranean as well as Europe that includes four hydrologic river types, according to 3 their natural flow regime: main stem rivers, stable streams, seasonal streams and 4 temporary streams. The relationships between flow regime and fluvial and riparian 5 habitats were studied at reference and hydrologically-altered sites for each of the four 6 types. Flow regime alteration was assessed using two procedures: 1) an indirect index, 7 derived from variables associated with the main hydrologic pressures in the basin, and 82) reference and altered flow series analyses using the Indicators of Hydrologic 9 Alteration (IHA) and the Indicators of Hydrologic Alteration in Rivers (IAHRIS). 10Habitats were characterized using the River Habitat Survey (RHS) and its derived 11Habitat Quality Assessment (HQA) score, whereas riparian condition was assessed 12 using the Riparian Quality Index (RQI) and an inventory of riparian native/exotic 13 species. Flow stability and magnitude were identified as the main hydrologic drivers of 14 the stream habitats in the Segura Basin. Hydrologic alterations were similar to those 15 described in other Mediterranean arid and semiarid areas where dams have reduced flow 16 magnitude and variability and produced the inversion of seasonal patterns. Additionally, 17 the Segura Basin presented two general trends: an increase in flow torrentiality in main 18 stems and an increase in temporality in seasonal and temporary streams. With the 19 indirect alteration index, main stems presented the highest degree of hydrologic 20 alteration, which resulted in larger channel dimensions and less macrophytes and 21 mesohabitats. However, according to the hydrologic analyses, the seasonal streams 22 presented the greatest alteration, which was supported by the numerous changes in 23 habitat features. These changes were associated with a larger proportion of uniform 24 banktop vegetation as well as reduced riparian native plant richness and mesohabitat 25 density. Both stream types presented consequent reductions in habitat and riparian 26 quality as the degree of alteration increased. However, stable streams, those least 27 impacted in the basin, and temporary streams, which are subject to great hydrologic 28 stress in reference conditions, showed fewer changes in physical habitat due to 29 hydrologic alteration. This study clarifies the relationships between hydrologic regime 30 and physical habitat in Mediterranean basins. The hydrologic and habitat indicators that 31 respond to human pressures and the thresholds that imply relevant changes in habitat 32 and riparian quality presented here will play a fundamental role in the use of holistic 33 frameworks when developing environmental flows on a regional scale. 34 2

Random forests to evaluate biotic interactions in fish distribution models

“…A more regional approach would be needed to validate the obtained results across different catchments in the Jucar River Basin District to gain more insight on habitat requirements of the considered fish species. However, samples from different rivers in nearly natural conditions are difficult to collect given the high degree of hydromorphological alteration of Mediterranean rivers (Belmar et al, 2013;Feio et al, 2013) and the sensitive state of the fish (Crivelli, 1996;Baillie et al, 2004).…”

Contributions from limnology to reservoir management

“…Además, a menudo dan lugar a un patrón temporal de caudales inverso al natural, con altos caudales en verano y bajos caudales en invierno Belmar et al, 2010), modificando las cadenas tróficas y la productividad del ecosistema fluvial (Wootton et al, 1996). Cuanto mayor sea la intensidad de la alteración mayor será el efecto sobre el número de especies (Carlisle et al, 2012), sobre la calidad del hábitat y del bosque de ribera (Belmar et al, 2013). Los embalses hidroeléctricos, a menudo causan importantes variaciones del caudal turbinado a escala diaria, e incluso semanal, en respuesta a los picos de demanda de consumo eléctrico (Prats et al, 2009), reduciendo el hábitat efectivo disponible y la productividad acuática (Poff et al, 1997).…”

“…En la cuenca del Ebro los embalses situados en tributarios hacia el sur, en la zona mediterránea, modifican de forma más importante el régimen hidrológico que los situados en la zona atlántica, húmeda . En ríos de zonas áridas y altamente reguladas como la cuenca del Segura, se pueden encontrar dos tipos de tendencias: en ríos permanentes se produce un aumento de la torrencialidad de los caudales; mientras que en los cursos de agua temporales, los períodos de circulación de agua se hacen aún más raros (Belmar et al, 2013).…”

Hydrological Signatures Based on Event Runoff Coefficients in Rural Catchments of the Iberian Peninsula

“…Moreover, similar weaknesses were noted by D' Ambrosio et al (2017) in relation to the reduced number of catchments and attributes analyzed, which must also be recognized in our study. However, we would like to highlight that (i) abundant literature exists showing daily, monthly, and annual stream flows (mainly quantiles and statistical moments) and their regionalization for large gauged and ungauged catchments (Sanborn and Bledsoe, 2006;Alcázar and Palau, 2010;Belmar et al, 2013), but there is a notable gap at the event scale and for small catchments (Merz et al, 2006;Norbiato et al, 2009), and (ii) for a small group of simple features of the catchments, representative runoff coefficients could easily be estimated. In order to improve the statistical performance, more effort should be made to contrast the results by adding new catchments in different climatological areas of the IP, as well as by enlarging the data series.…”

“…Consequently, land-use changes may create higher vulnerability in the management of water resources (Belmar et al, 2011). Numerous studies describe the possible alterations of runoff regimes (e.g., see Batalla et al, 2004;Magdaleno and Fernández, 2011;Belmar et al, 2013;Wang et al, 2017). However, comparative analyses at the event scale and in medium and small catchments are less common, despite the fact that these catchments are usually located in the headwaters of larger catchments.…”