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Modeling Ecosystem Services From River Flows - Does It Help To Understand Conflicts?

Congress: 2015
Author(s): Di­dac Jorda-Capdevila, Beatriz Rodri­guez-Labajos, Mónica Bardina
Universitat Autònoma de Barcelona1, Agència Catalana de l'Aigua2

Keyword(s): Sub-theme 14: Valuing water: monetary and non-monetary dimensions,
AbstractThe hydrological and ecological impacts of damming rivers is well-known (Poff et al. 1997). Hydrological alterations produce economic impacts (e.g., Martin-Ortega et al. 2012), some of them related to non-marketed goods and services (e.g., González-Cabán and Loomis 1997; Ojeda et al. 2008). The economic relevance of water-related ecosystem services (ES) is acknowledged at the global level (Russi et al. 2012). However, local studies are still scarce, especially regarding the management of water flows. In particular, the understanding of the dynamics of appropriation of instream flows-related ES needs to be addressed. In order to fill this gap, we propose a methodology, based on participatory modeling, for the valuation of ES from water flows. While testing this innovative methodology for the particular case of the Ter River, in Catalonia, we also explore its potential to understand socio-environmental conflicts in the context of alternative management scenarios.

In a relatively small area (3,010 km2), the Ter River basin offers the possibility of studying practically all the typical intra- and inter-basin socio-economic processes linked to environmental flows in a Mediterranean context, such as water transfers, small hydropower conflicts and expansion of irrigated areas. In the middle course, two main dams regulate floods and store water reserves. The dams also divert 39-81 % of the annual water inflow to supply domestic and industrial uses in the metropolitan Barcelona, out of the Ter River basin. The hydrological alterations caused by those dams have been deteriorating the ecological state of the Lower Ter (Benejam et al. 2010; Boix et al. 2010), also impairing the ecosystem services provided (Jorda-Capdevila and RodrĂ­guez-Labajos, 2014).

The methodology presented encompasses two consecutive models. The first one is a water management model that uses the Water Evaluation And Planning (WEAP) software. Different scenarios of water management are introduced, eliciting water demands and priorities of usage based on participatory methods. The results provide the distribution of water flows (expressed in Hm3/year) through water courses and demand sites. These water flows can either be diverted for different uses (e.g., irrigation, hydropower, and domestic supply) or remain as instream flows (and then used for e.g., kayaking, angling, and ecosystem maintenance).

The second model is an ES-production model. Using the water flows previously obtained as an input, it calculates the value of indicators (expressed in a range 0-1) related to the performance of different ES according to the corresponding flow level. These values can be interpreted as an indication of the suitability of ES provisioning levels (i.e. 0 means 'null', 0.5 'minimally acceptable' and 1 'optimum' values). A crucial step for the construction of this model is the design of ES-production functions, also based on stakeholders' experience and requirements.

Three management scenarios are assessed (Table 1). They have been designed from a compilation of official documents, several interviews to water managers, and a survey to 28 organizations claiming for a better management. In the 'business as usual' (BAU) scenario, the planned environmental flow regime for the Lower Ter (ACA 2009) is not implemented and a major water transfer to Barcelona remains as the major withdrawal of the catchment. The 'compatibility of uses' (COM) scenario gives priority to the environmental flows and represents decreased inter-basin water transfer and irrigation needs. Finally, the 'ecosystem priority' (ECO) scenario clearly bets on intra-basin uses by discharging up to 89 % of water inflows from the reservoirs; this benefits the ecological uses and, indirectly, the run-of-the-river hydropower production.

Table 1. Water flows resulting from the WEAP model in annual averages (minimum, maximum, and percentages in relation to the total average of water inflows into the reservoir). The percentage of diverted water for hydropower production ranges depending on the hydropwer plant.

These results are inputted into the ES-production models, one for each ES analyzed: intra-basin domestic supply, water transfer to Barcelona, hydropower, irrigation, historical canals, wetlands and river ecosystem maintenance, safeguarding the salt edge away, elver and trout fishing, aesthetics of the waterscape in Girona city, and familiar and freestyle kayaking. The outcomes shed light on several aspects of interest for water management. The model allows visualizing the level of provision of specific ES along the river. The variation of the ES provision along the year comparing dry, humid and normal years or different water management scenarios can also be drawn. In addition, tradeoffs and synergies can be identified comparing the production of different ES under certain conditions.

In relation to potential conflicts in the Lower Ter, our model offers several insights. First, different ES compete for water flows, interfering in spatial coexistence. Hence ES localization pinpoints competition hotspots that could be managed. A good example is Girona city, where hydropower production coexists with tourism and local recreation. Second, modeling ES spots critical moments of competition among ES over the hydrologic year and for rainy, dry and normal years. In spring and summer, demands for irrigation enhance the water availability for kayaking and the preservation of wetlands. Finally changing the priorities among water uses shows which use conditions the provision of the others. In particular, the water transfer to Barcelona drags the bulk of water flows, impacting the production of the rest, especially during dry years. Hydropower production does not particularly threat the river ecosystem when the transfer is low.

The model here presented is a useful tool to understand the complexity of managing rivers that frequently suffer natural droughts and intense human pressures, as the case of the Ter River, in the Mediterranean basin. Multiple stakeholders are involved to incorporate their requirements in terms of water flows and to design management scenarios preferable for them. This paper shows sound tradeoffs in specific stretches and at specific moments, giving an idea of where and when a conflict can break up under the controversial BAU scenario. COM and ECO scenarios appear as management alternatives with the aim at sharing the benefits that a well-preserved river provides. Making these results explicit improves transparency hence facilitates informed negotiation for a better river management.

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