Guidance on Ecological Flows (Eflows)

Case study template

Guidance on Ecological Flows (Eflows)

Template for Case Studies

February 2014

Table of Contents

Table of Contents

Title of the case study

Executive summary

General information

2.1.Objective of the Case study......

2.2.Policy and management context...... 4

Detailed information...... 4

3.1.Practical Tasks (in case of methods and/or procedures)...... 4

3.2.Temporal and spatial scales...... 4

3.3.Type of analysis or tool...... 4

3.4.Information and data requirements...... 5

3.5.Testing of results...... 6

3.6.Current application of the method/initiative...... 7

3.7.Learned lessons - Conclusions – Recommendations for application within the concept of Eflows 7

Contact information...... 7

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Estimating the minimum ecological flow downstream of the Gadouras reservoir (Rhodes Island, Greece) for conserving the local Gizani (Ladigesocypris ghigii) populations

Executive summary

The project proposed a modified flow regime for river Gadouras (Rhodes Island – Greece) in order to maintain necessary levels of water in instream pools found to be critical for the survival of a particular endemic fish species (Ladigesocypris ghigii – c. Gizani), after a reservoir construction and operation. Expert judgment and hydraulic modelling were utilized. Four sites upstream of the dam and 5 sites downstream were selected for sampling fish and record quantitative and qualitative data. The Mike11 hydraulic model was used to simulate a particular river stretch and propose the modified ecological flowregime. Telemetry stations were installedin two sites downstream of the dam. Moreover, adaptivee-flow management has been proposed according to wet/dry periods, wet/dry years and water level fluctuations in the artificial lake. Through field surveys, it was estimated that a threshold water depth of 20cm is necessary to act as an alarm and initiate the ecological flow discharge from the dam. The rate of water withdrawal in dry periods for the area has been observed to be 3cm/day and the mean-depth of the pools was 1.5m - 2m. This indicated that in dry periods of the year, eflow of slightly less than 300m3/h (calculated as the necessary flow to retain more than 20cm depth in the pools) should be released from the dam for 6 consecutive days. With this as a starting point, hydraulic and hydrological data were integrated in the Mike11 software in order to simulate dry/wet years, different water levels in the reservoir, wet/dry periods, different water needs and the changes provoked by these different flow regimes (+/- 30% water supply). During the wet period, the telemetry stations monitoring the water levels have been used as warnings when water falls to the critical level of 20 cm in order to release eflow in the same concept.

General information

MemberState(s): EL

RBD(s): 14

Location:AegeanIslands

Time period (start/end): 10/2011 to 12/2012

2.1.Objective of the Case study

Four major objectives were included in the Gadouras dam case study: (i) Monitoring of the current state of Gizani populations downstream of the Gadouras reservoir, (ii) assessment of the minimum flow requirements of the Gizani populations for maintaining their functionality throughout each year and ensure their survival during low flow (near-dry or dry) summer conditions, (iii) proposing an eflow schedule to the dam operator according to the previous eflow assessment, (iii) pilot implementation of a flash flood, monitoring fish responses and further readjustment of the eflow proposal.

2.2.Policy and management context

According to the Joint Ministerial Decision 49828/2008, ecological flows should be assessed and provided downstream of hydropower plants or reservoirs for ensuring ecosystem integrity and prevent deterioration of aquatic communities. Although ecological flows are acknowledged as a crucial part of an Environmental Impact Assessment in regulated river systems, the current definition of ecological flows according to the Greek legislation is only hydrological, without addressing the requirements of aquatic communities.

Ladigesocypris ghigii (Gizani) is a RhodesIsland endemic fish species, included as a priority species in the Habitats Directive 92/43/EEC, mentioned in the Red Book of Endangered Species of Greece and also protected by the Greek Presidential Decree 67/1981. The particular case study was part of a LIFE project including, inter alia,public participation in informational meetings, brochures and other promoting material enhancing local awareness about Gizani populations.

Detailed information

3.1.Practical Tasks (in case of methods and/or procedures)

The methodology adopted by the Hellenic Centre for Marine Research (HCMR) resulted in an eflow schedule, applied by the dam operator, with relative adjustments for wet/dry periods, wet/dry years and water level fluctuations in the artificial lake. This schedule has been applied annually for the protection of the Gizani populations.

3.2.Temporal and spatial scales

Gadouras is a typical Mediterranean temporary river, which becomes dry during almost every summer. The current study was conducted to ensure the survival of the Gizani populations under critically reduced (near-dry or dry) flow conditions of the summer period, by maintaining more than 20cm depth in specific instream pools,through an recurrent eflow release by the dam operator. The study addresses the needs of Gizani populations downstream of the reservoir and the schedule is annual with adjustments proposed for wet/dry years or unexpected declines in the water level.

3.3.Type of analysis or tool

Through field surveys, it was estimated that more than20cm water depth is necessary to maintain the species populations in the pools of the river in near-dry flow conditions. In close collaboration between the HCMR and the dam operators, the methodology applied included the following steps:

1. Establishment of two telemetry stations for the continuous monitoring of water levels - The first station was established in Rhodes 1 (1km downstream of the dam) and the second in Rhodes 2 (3km downstream)(fig. 1).
2. Estimation of the time necessary for the water to reach and fill the pools, which provide habitat for the Gizani populations - For this purpose, the dam operators opened the eflow valve for 6 consecutive days and continuous measurements in combination with the data provided by the two telemetry stations indicated that with the standard flow provided by the eflow valve, the water filled “Rhodes 1” in 2.5 days and “Rhodes 2” in 4 days.
3. Estimation of the time for water withdrawal from the two sites (Rhodes 1 and 2) - The minimum time for withdrawal was observed in Rhodes 2 and calculated at 3cm/day. Considering that the mean depth of the pooling areas is 1.5m to 2m, it was estimated that these pools, which constituteGizani’s habitats need 50-60 days to dry completely. This indicated that during the dry period (May-October), flow release from the e-flow valve should be applied every 40 days to prevent desiccation of the pools.
4. Input of field data into the Mike11 hydraulic model, calibration and estimation of the necessary flow to retainmore than 20cm water depth in Gizani’s pools - an eflow of approx. 300m3/h should be released from the dam for 6 consecutive days, according to the water level in the reservoir and the period of the year, in order to counterbalance the water withdrawal in the pools (fig. 2).

3.4.Information and data requirements

Physicochemical measurements regarding (total hardness, HCO-3CO2-3, Ca, Mg2+, Na-, K+, Cl-, totalP, totalN, SiO2, PO3-4, NO-2, NO2-3, NH+4 were undertaken in four sites upstream, three sites downstream and one site located inside the reservoir for estimating the general water quality of the river length. Field surveys from experienced ichthyologists were undertaken in the same sites in order to assess the abundance of Gizani populations and address their minimum water flow requirements (more than 20cm water depth in the pools). Application of the Mike11 software enabled the visualization of the consequences of the different flows applied to the river bed and the pool areas and the estimation of the flow, which should be released in order to meet the Gizani’s needs.

3.5.Testing of results

Monitoring by ichthyologists was undertaken at each site, one year after application of the eflow schedule by the dam operator. Gizani populations were well maintained during the dry season and fish survival was ensured. In combination with the eflow application, an artificial introduction of Gizani populations from the upstream parts of the river has been proposed to be applied during the wet season. Monitoring is currently performed in an annual basis by local or HCMR experts.

3.6.Current application of the method/initiative

The proposed eflow schedule is being routinely applied by the dam operator, with adjustments for wet/dry periods or wet/dry years. This method has not been replicated yet in other WBs.

3.7.Learned lessons - Conclusions – Recommendations for application within the concept of Eflows

This method provides a baseflow required for a specific fish species, with a slight divergence from a typical eflow assessment. However, it is a good alternative and can be replicated in similar semi-arid environments, typical of the mediterranean region, where desiccation of water is a critical issue for the survival of aquatic communities. There are no limitations for the application of the particular method. The telemetry stations are not as expensive as they were in the past and their establishment and data feedback is much easier.Moreover, as cost-effectiveness is another critical issue of an eflow assessment, this method can be utilized as a cost-effective alternative, when funding for more complicated assessments is insufficient.

Lessons learned and issues to be improved for future applications:

1. The application of the method, although not directly linked to the requirements of the Habitats Directive 92/43/EEC, is expected to lead to a “favorable conservation status” for the populations of Gizani, as described in the Directive.
2. The proposed ecological flow was not compared to natural/historical hydrological data due to lack of such long-term records for the particular river. However, a combination of the current method with a comparison to natural/historical records(where available) is expected to raise the method’s accuracy.
3. Geomorphic effects of dam in the pools were not estimated in the current study
4. Hydrological effects of the proposed eflow were not estimated beyond 3km (from Rhodes 2 to estuaries), as the river becomes naturally dry beyond that point. Moreover, the target of the study was to maintain the populations of Gizani and no such populations were observed further downstream of Rhodes 2 during the biological sampling. However, in a possible replication of the case study, the whole river length could be accounted for more “safe” eflow proposals.

Contact information

In case you request further information, please access:

• Elias Dimitriou, , +302291076349
• Maria Stoumboudi, , +302291076392
• References: Reports in Greek

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