Longitudinal connectivity loss in a riverine network: accounting for the likelihood of upstream and downstream movement across dams
Disruption of longitudinal connectivity is a major concern in most of the world´s rivers. Approaches based on graph theory have proven to be a suitable tool for analysing functional connectivity. However, previous applications of graph-based connectivity methods to river systems have been oversimplified in that they have treated potential barriers as binary features and rivers as symmetric networks. We here apply a network analytical approach in which (a) upstream and downstream connectivity are considered so that fish passability values across dams are asymmetrical, and (b) it is possible to consider a continuous range of passability values for every dam. We build on previous and widely used connectivity metrics (Probability of Connectivity, PC), which here are generalised and adapted toward that end. We compare the results of our approach with those that would be obtained under the more simplified assumptions of symmetric movement and of barriers as binary features. We want to prove if there are substantial differences between considering or not the asymmetry in river networks. The application of symmetrical and asymmetrical PC highlights major differences between the upstream connectivity versus the downstream connectivity. We provide our methods in a free software package so that they can be used in any other application to riverscapes. We expect to provide a better graph-based approach for the prioritisation of the removal or permeabilization of artificial obstacles as well as for the preservation of target river segments for connectivity conservation and restoration.
KeywordsLongitudinal connectivity Fish passability Graph theory Directional networks Asymmetric dispersal Riverscapes
- Bjornn TC, Peery CA (1992) A review of literature related to movements of adult salmon and steelhead past dams and through reservoirs in the Lower Snake River. Technical Report 92–1, US Fish and Wildlife Service, Idaho Cooperative Fish and Wildlife Research Unit, University of Idaho, MoscowGoogle Scholar
- CHD (2009) Plan hidrológico del Duero. Plan hidrológico de la parte española de la demarcación hidrográfica del Duero propuesta de proyecto de plan hidrológico de cuenca. EspañaGoogle Scholar
- González Fernández G, Pérez Cardenal D, Miguelez Carbajo D, Gallego García R, Fernández Suárez R, Álvarez Durango E, Canal Rubio P, Roa Álvarez I, Rosa Cubo E, Seisdedos Fidalgo P (2010) Diagnóstico de la conectividad longitudinal en la Cuenca del Duero. Ministerio de Medio Ambiente, Medio Rural y Marino. Available on http://www.chduero.es/acciona5/metodologia/ic.pdf
- Gough P, Philipsen P, Schollema PP, Wanningen H (2012) From sea to source: International guidance for the restoration of fish migration highways. Regional Water Authority Hunze en Aa´s. The NetherlandsGoogle Scholar
- Hilty JA, Lidicker WZ Jr, Merenlender A (2012). Corridor ecology: the science and practice of linking landscapes for biodiversity conservation. Island PressGoogle Scholar
- Junta de Castilla y León (1997) Estudio de las poblaciones piscícolas del río Cega (Segovia). Technical Report: Estudios Biológicos, MadridGoogle Scholar
- Kondolf GM, Boulton AJ, O’Daniel S, Poole GC, Rahel FJ, Stanley EH, Whol E, Bång A, Carlstrom J, Cristoni C, Huber H, Koljonen S, Louhi P, Nakamura K (2006) Process-based ecological river restoration: visualizing three-dimensional connectivity and dynamic vectors to recover lost linkages. Ecol Soc 11(2):5CrossRefGoogle Scholar
- Nicola GG, Elvira B, Almodovar A (1996) Dams and fish passage facilities in the large rivers of Spain: effects on migratory species. Large Rivers 10:375–379Google Scholar
- Santiago JM, García de Jalón D, Alonso C, Solana J, Ribalaygua J, Pórtoles J, Monjo R (2015) Brown trout thermal niche and climate change: expected changes in the distribution of cold-water fish in central Spain. EcohydrolGoogle Scholar
- Saura S, Rubio L (2010) A common currency for the different ways in which patches and links can contribute to habitat availability and connectivity in the landscape. Ecography 33:523–537Google Scholar
- Saura S, Torné J (2009) Conefor Sensinode 2.2: a software package for quantifying the importance of habitat patches for landscape connectivity. Environmental Modelling & Software 24: 135–139.Google Scholar
- Saura S, Torné J (2012) Conefor 2.6 user manual (April 2012). Universidad Politécnica de Madrid. Available at http://www.conefor.org.
- Segurado P, Branco P, Avelar AP, Ferreira MT (2014) Historical changes in the functional connectivity of river based on spatial networks analysis and the past occurrences of diadromous species in Portugal. Aquatic SciGoogle Scholar