2.29 Sand Encroachment by Hálslón Reservoir

2.29 - Sand Encroachment by Hálslón Reservoir

 

 

 2.29 Revegitation area east of Hálslón reservoir.        2.29 Sand fences      2.29 Sand traps and revegetation

The above images demonstrate countermeasures taken against sand encroachment by Hálslón reservoir.  The pictures show sand traps, sand fences and revegetation.  Click for larger images.

 

 

Progress

 

The report, on environmental impact assessment of Kárahnjúkar power plant, states that it is important to establish a monitoring system along all edges of Hálslón reservoir since considerable erosion is to be expected in the first years/decades after its formation with the associated risk of aeolian deposits reaching grown areas. In accordance, Landsvirkjun has monitored erosion proceedings at Hálslón reservoir in various ways. Coastal areas have been walked and mapped to include erosion areas and mineral composition of the reservoir coast, erosion at the highest reservoir level has been monitored and aerial photos have been taken regularly. Also, the coast has been geodetically measured in several transects which helps to monitor the long-term development of the coast. Simultaneously, aeolian deposition is monitored above coastal areas. In addition to closely observing the progress of the coastal areas, erosion and encroachment defences have been installed (see pictures above) and the vegetation strengthened east of Hálslón reservoir so that it can better survive the blowing sand. A method to clean sand of grown land has been developed. In 2014 the Soil Conservation Service of Iceland (Landgræðsla ríkisins) was asked to do assess aeolian deposits at Hálslón reservoir and at the same time design a system to monitor long term aeolian depositions. Concurrently three measuring stations were set up at Kringilsárrani area to monitor and measure aeolian deposition.

Further information on countermeasures and observations at Hálslón reservoir can be found in reports under the "Further reading" tab (only in Icelandic).

 


Findings from inspection 2016

The 2016 summer inspection of aeolian deposition was performed on July 5 - 7.  Since neither inspection of aeolian deposition areas nor automatic measurements indicated big changes between the years 2014 and 2015 less thorough inspection than before was planned for 2016.  On the east shoreline of Hálslón inspection was limited to areas were aeolition had been detected earlier.  In Kringilsárrani area the whole shoreline was inspected as before.

No sign of new aeolian deposition was detected on the East shoreline of Hálslón reservoir that is by Lindabunga and Kofaalda. The effect of vegetation reclamation was however obvious causing previous signs of aeolian deposition less evident than before.

The northernmost area of Kringilsárrani did not seem to have changed much either from 2015.  Two rather small deposition areas had appeared about 400 m. north of Hraukar moraines.  It appeared to consist of mixture of material from the reservoir  bed and banks.

The austomatic measuring station at the sand pile south of Hraukar moraines detected three main deposition events, one in the fall of 2015 and two in the summer of 2016.  It appeared to be material already deposited behind the fences rather than new material from the reservoir bed.  The sand pile north of the sand fences had grown to the northeast.

Spreading of aeolian deposition had increased somewhat in the area north of Syðri Hraukar moraines since 2015 although deposited material seemed to have lessened in some locations.  This indicates that already deposited material is drifting around rather than more material is being added.

2.29_mynd1_2017
Figure 1. Aeolian deposition areas by Hálslón reservoir:  a) by Lindabunga, b) by Kofaalda, c) northernmost part of Kringilsárrani, d) by Hraukar moraines and e) north of Syðri Hraukar moraines.  (obs. size of areas is exaggerated to show location.  New deposition areas from 2016 are marked yellow.

 

Updated: June 28 2017
Source: Landsvirkjun (2017)

Monitoring Protocol



Metrics: What is measured

Coastal areas of Hálslón reservoir in spring and autumn. Areas where sand has drifted from the coast are recorded, their size estimated/measured as well as sand thickness (project effect: direct).

Monitoring Protocol

Visual monitoring. Data gathered after the reservoir is filled. Regular visits will be made to the area following storms.

Targets

No aeolian deposition east of the reservoir.

Possible countermeasures

Landsvirkjun initiates countermeasures to prevent aeolian deposition.

 

Updated: January 6 2016 

Metrics - changes from original plans

At the annual meeting of the initiative on May 6 2015 the following proposed amendment was passed.

What is measured

   Original text Amended text
  Volume of aeolian deposition
from the east coast of the reservoir.
Coastal areas of Hálslón reservoir in spring and autumn.
Areas where sand has drifted from the coast are recorded,
their size estimated/measured as well as sand thickness
(project effect: direct).

 

Rationale for amendments

The monitoring protocol states analysis of volume of aeolian deposition east of the reservoir. It is technically difficult and not realistic to measure volume but possible to estimate area. In addition, the protocol only mentioned the East coast of the reservoir but Kringilsárrani area is also monitored and should be included in the monitoring protocol.

In fourth phase of the initiative the numbers of the indicators were changed. This indicator was originally number 26.2 and is referenced as such in early documents of the project.

Baseline

Figure 1. BaselineThe map to the right is a rendering of the reservoir in beginning of June on an average year. The water level is then 580 meters above sea level or 45 meters under the highest water level. During this period 16 km2, of the reservoir bed,  are above water level on the east side of the reservoir. The right side of the map, shows the reservoir in early August during an average year. The water level is then 615 meters above sea level or 10 meters below the highest water level.  During this period 4 km2 of the reservoir bed are above water level east of the reservoir and the potential for wind erosion has decreased. The thickness of the soil is estimated to be in average about 2-2.5 meters east of the reservoir. The area will be categorized according to land slope in order to evaluate beforehand where it is most likely that sand piles will form.

Research are ongoing on the stamina of the vegetation in the eastern part against aeolian deposition and how to react to possible deposition of minerals.

 

Rationale for Indicator Selection

Part of the reservoir shoreline area or approximately 15 km2 is covered with around 2.5 m thick soil coated with thin layer of vegetation. With time this volcanic soil can wash into the reservoir through water erosion and wave action, but also drift to surrounding area causing soil thickening and even vegetation loss.

With time wave erosion removes soil from Hálslón reservoir shoreline.  The erosion rate is dependent on the slope of the shore area and the intensity of wave action. The erosion rate is highest on steeply sloping shore areas and slowest on flat plains on the shore.

On these gentle sloping planes the vegetation might disappear after a few years of reservoir operation, leaving only soil. On steeper shoreline areas erosion slumps can form in the soil before it is removed by wave erosion.  These conditions may prevail during the first one or two decades of reservoir operation. 

During dry storms from the south and southwest the exposed dry soil may be picked up by the wind and the largest particles drift onto adjacent vegetated area forming sand piles above the highest water level. In wetlands this risk is however greatly reduced. The east side of the reservoir is specially prone to aeolian deposition.  On the west shoreline, windblown sand drifts chiefly to the reservoir during strong wind from South or South-West and therefore no sand piles are formed.

While soil prone to erosion remains, various operations are planned to prevent aeolian deposition to damage vegetated areas in Vesturöræfi wilderness. Sand traps were setup along vegetated areas by the east shoreline of the reservoir.  Irrigation, dust binding and sand fences are planned as means to control drift of soil. 

Measures to strengthen vegetation east of the reservoir, are also being considered.




 

Further reading

Reports on aeolian deposition published by Landsvirkjun  (only in Icelandic)

 

 

LV_2016_119_forsidaÚttekt og mælingar á áfoki við strönd Hálslóns -
LV-2016-119

Click here to download report

 

 

 

Úttekt og mælingar á áfoki við strönd Hálslóns - Áfangaskýrsla 2015. 
Landsvirkjun report no:  LV-2015-104

Click here to download report

 

 

Vöktun á áfoki í Kringilsárrana - 2.29Vöktun á áfoki í Kringilsárrana
Landsvirkjun report no:  LV-2014-121

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Að beiðni Landsvirkjunar var gerð úttekt á áfoki frá lónstæði Hálslóns og hannað úttektarkerfi fyrir vöktun á áfoki til framtíðar. Vöktunarkerfið byggir á ljósmyndum sem teknar eru með reglulegu millibili meðfram lónsborði Hálslóns. Þá er metin útbreiðsla áfokssvæða sem hafa þegar myndast og þykkt áfoks mæld. Úttekt fór fram við austurströnd Hálslóns og í Kringilsárrana í júlí 2014. Niðurstöður úttektarinnar sýna að tvö áfokssvæði eru við austurströnd Hálslóns, við Lindarbungu og Kofaöldu og eru þau bæði yfir 1 ha að stærð. Í Kringilsárrana eru þrjú megin áfokssvæði, norðan Syðri Hrauka er um 1,8 ha samfellt svæði, í vík rétt sunnan Hrauka er að myndast áfoksgeiri, auk þess sem áfok er á nokkrum svæðum við fokgirðingarnar nyrst í Rananum. Mesta áfokið er í víkinni sunnan Hrauka, á rúmlega 0,2 ha svæði með að jafnaði rúmlega 4 cm þykku áfoki.Úttekt og mælingar á áfoki við strönd Hálslóns
Landsvirkjun report no:  LV-2014-094

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Að beiðni Landsvirkjunar var gerð úttekt á áfoki frá lónstæði Hálslóns við strönd Kringilsárrana. Nyrst á Rananum má sjá merki um áfok frá lónstæði Hálslóns en mest var áfokið þó við austurströnd Kringilsárrana á svæðinu milli Hrauka og SyðriHrauka.

Mat á áfoki við strönd Kringilsárrana
Landsvirkjun report no:  (LV-2014-005)

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Í þessari skýrslu er kortlagningu strandar við Hálslón sumarið 2011 lýst og gerður einfaldur samanburður við fyrri athuganir á ströndinni. Rofkort af ströndinni við Háls og Kringilsárrana fylgja skýrslunni og landmælingasnið frá árinu 2009.

Hálslón 2011: Kortlagning strandsvæða
Landsvirkjun report no:  (LV-2012-007):

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Í greinagerð Landsvirkjunar og Landgræðslunnar um rofvarnir og gróðurvernd við Hálslón er gerð grein fyrir hvað hefur áunnist varðandi mótun og þróun aðgerða sem líklegt er að dugi til að vernda gróður fyrir sandfoki.
Greinargerð Landsvirkjunar og Landgræðslunnar um rofvarnir og gróðurvernd við Hálslón

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