The Test Cases of Guma and Vadocondes are situated on the Duero river, which is located in the northwestern part of Spain. The source of the Duero river is in the Castilla y León region, which it crosses from East to West to then enter Portugal where it finishes its way into the Atlantic ocean. The total length of the river is about 900 km and the catchment area is 98,400 km2. The presence of hydropower plants (HPPs) in the Duero river is quite common, with 140 small hydropower plants (below 5 MW) and 23 large HPP situated on the Duero river.
The hydrology of the Duero river on this zone is characterized by low flows in summer (regulated flow for irrigation mostly derived through channels) and medium-high flows during winter and early spring, associated with rainy season and snow episodes.
Upstream migration period for native cyprinids is from April to June, with mean monthly flow in the Guma-Vadocondes case of study reach, approximately between 15 and 30 m3/s.
Guma & Vadocondes hydropower plants
Boths, Guma and Vadocondes, are run-of river hydropower plants with an installed capacity of 2.25 MW (Guma) and 1 MW (Vadocondes) respectively. Each has 2 Kaplan turbines installed. Guma and Vadocondes are separated only by 3.9 km of the Duero river. The mean annual discharge is 17.6 m3/s, varying between 6 m3/s and 48.9 m3/s as a minimum and maximum mean annual discharge.
The Case Study site and relevant water body of the Duero reaches from 28 km upstream of the Guma HPP to 16 km downstream of the Vadocondes HPP. The two HPPs are placed in Guma and Vadocondes villages (Duero River, Burgos province, Central-North of Spain). The distance between both HPPs is about 3.9 km –the Guma dam is close to the end of the Vadocondes reservoir– and they are operated coordinately (flow and time) by the same company (SAVASA). Vadocondes reservoir has a length of about 2 km and Guma's reservoir 3 km (the influence of slow waters), with a maximum depth in Guma of about 8 meters and in Vadocondes of 2.5 meters. The bypass reach in both cases is about 150 m, including upstream devices, specifically pool and weir fishway in Guma and vertical slot fishway in Vadocondes.
Layout of the Vadocondes and Guma HPP
|Capacity||Guma: 2.25 MW,
Vadocondes: 1 MW
|Head||Guma: 8.85 m,
Vadocondes: 3.75 m
|Inter-annual discharge||17.6 m³/s|
|2 Kaplan turbines at each HPP|
The Operator: SAVASA
SAVASA (Salto de Vadocondes S.A.) is a small hydropower company which operates the HPPs of Guma and Vadocondes. It has always shown an interest for fish conservation, being a pioneer on this region implementing devices for fish movement and the improvement of the knowledge about fish behaviour building, for example, a scientific fish swimming flume on its installations.
Pressures on the water body's ecosystem
Several dams with different purposes upstream and downstream of the two HPPs pose a problem for the continuity of the water body and thereby for fish migration. The native fish species are in decline and several alien species are appearing and/or increasing in number. The flow is highly regulated for irrigation and hydropower uses and there are a lot of artificial lentil habitats due to the presence of dams, which has an effect on the hydrology. There is a heavy agricultural use in the area with a significant use of agrotoxins, which leak into the water. Several dams block the sediment transport, especially since there is no law that enforces an improvement of the situation.
Test Case topics
The river is dominated by small and medium size reophilic native cyprinids like Iberian barbel (Luciobarbus bocagei), northern straight-mouth nase (Pseudochondrostoma duriense), Northern Iberian chub (Squalius carolitertii) and Pyrenean gudgeon (Gobio lozanoi). All of them are suffering a decrease in their populations (specially nase, wich is an endemic species) and allien species are increasing their presence (mainly Alburnus alburnus).
The main facilities for upstream migration are the fishways built on each dam (all native species are potamodromous). At Guma, it is a pool and weir fishway, with submerged notch with bottom orifice. It has a slope of 8.77 % and covers a trial height of 8.85 m. Vadocondes has a vertical slot fish pass with a trial height of 3.75 m. Both have supplementary attraction flow into the fishway entrance.
|Iberian barbel, northern straight-mouth nase, Northern Iberian chub|
|Vadocondes dam: vertical slot fishway|
|Guma dam: pool and weir fishway|
Due to the hydropower plant type (over the dam and run-of-river type), there is no legal requirement for ecological flow. Nonetheless, fishways always must have enough flow for operating and therefore the downstream by-pass of the river always maintains a minimum flow of 0.25-0.50 m3/s.
Research objectives and tasks
This hydropower plant type (run of river) is quite common on the main Spanish river basins. The work at the Test Case sites aims at improving the knowledge on the impacts this type of HPP has on fish migration and location of ascent paths. Different flow configurations through the turbines and fishway-attraction flow will be tested to maximize the relationship between fish upstream movement and hydropower production. Also, fish passage through turbines and their survival using different turbine configurations will be an important result about HPP management and impact.
The research tasks and field studies conducted at Guma and Vadocondes are:
- Population and habitat analysis
- Analysis of the conceptual solutions and facilities for fish migration
- Assessment and improvement of fish mortality in the turbines
- Spawning areas and hydro-morphology to attain self-sustainable populations
- Migration facilities and attraction flow
- Hydraulic modelling of attraction flow
|Upstream & downstream migration|
|Turbine passage and fish survival|
Results and updates
Impressions from field work done at Guma and Vadocondes:
pictures: © GEA - Ecohidráulica