pilot study in albania (ulza case study)
TRANSCRIPT
Name & surname, institution Elvin Toromani, Forest faculty, Tirana
PILOT STUDY IN ALBANIA (Ulza case Study)
Regional webinar, November 18-19, 2020
Why Ulza catchment was selected?
The study region is within the catchment area of the Ulzareservoir and belongs to the Mat river basin.
Some data about Ulza reservoir:
• the average annual inflow in the reservoir is 1.274 million m³
• the total storage capacity is 170 million m³
Erosion in the basin is huge and the value of annual totalproduced sediments (erosion material on the catchment)is 1,8 million m³ (CNVP , 2014). Out of them 1,36 millionm³ annually are transported to the reservoir Ulza or 1.112m3/km2/year.Bathymetric measurements in 2013, showed that 75million m³ are deposited during the period from 1958-2013.
• In 2018 bathymetric measurements indicated that total storage volume, from1958 to 2018, was reduced of about 63 million m³ or with at least 26,2% of thetotal reservoir storage filled with sediment (Beta Studio – E.B.S Shpk 2019).
• Based on this study, taking into consideration the climate change scenarios, the mean annual sediment siltation could increase from 1 315 000 m3/year (RCP4.5 scenario) to 1 370 000 m3/year (RCP8.5 scenario) and the remaining lifespan of the Ulza reservoir would reduce from 134 to 119 years respectively.
• The estimated value of potential soil loss for Ulza catchment (35.45 tons/ha/year) is much higher than the mean annual rate of soil loss due to water erosion for the EU countries (2.46 t/ha/year).
LocationThe study area is located close to the reservoir on thesouthern part of the basin.
The study area encompass two neighboring catchments as follow:
✓Catchment 1………780 ha and
✓Catchment 2 …….. 490 ha
Topography and hydrography
Both catchments are exposed to north.
DEM of the catchment Slope of the catchment (degree)
Generally, slopes between 2º and 20º are dominant, while slopes between 20 º and 40º occurs partially.Within catchment 1 is delineated one stream that originated from the vicinity of village Bazi. This streamconsists of 2 parts that confluent near the mouth to the reservoir.Within catchment 2 there is 1 stream that origin near the top point. Beside it, there are few ephemeralstreams.
Climate
Ulza Dam is situated in the NorthMediterranean Hilly Climate Sub-Zone(Climate Division of Albania, in “Climate ofAlbania, published by Institute ofHydrometeorology of Tirana, 1984).
The annual amount of precipitation in the region for the period 1931-1965 in Burrel is 1148 mm.
The study area has a non-uniform distributionof the precipitation. Most of precipitation(about 70%) fall during the period October –March, while during the summer months(June – August) fall usually less than 10% ofthe yearly precipitations.
Time Rainfall Intensity (mm)
15 minutes 30-40
30 minutes up to 80
60 minutes up to120
120 minutes up to 152
180 minutes up to 161
GeologyFrom the geological point of view, the projectarea started to develop during the Mesozoikperiod.
Throughout the Middle Jurasic (J2), from 170to 145 million years ago were formed themagmatic ultrabasic rocks, basic andigneous/volcanic that are at the same timethe oldest rocks in the project area.
On the eastern side of the project area aredispersed the deposits of the Kenozoic period(Tortoninan & Pliocen) formed from 22 to 2.6million years ago.
The latest deposits are those formed duringthe Kuaternar period which has e geologicalage less than 2.6 million years and aresituated in the bottom of slopes andwatercourses that percolate the project area.
Soils
• Soils within the study area are divided on
1) Permeable soils:
• Chromic Cambisol
• Leptic Regosol
2) Impermeable soils
• Haplic vertisol
Land Cover/Use and vegetation
• The major part of the area is under thebroadleaved forest with a significantappearance of transitional woodland(bushland).
• In the upper part, there is agriculturalland and pastures.
• The western part of the catchment isdominated by bare land.
• The forest area is predominated bycoppice forests where Quercus cerris L.is mixed with Quercus frainetto Ten.,Carpinus betulus L., and Fraxinus ornusL. The understory is represented bybushes like Rosa canina, and groundvegetation.
Forest management unit and compartments
Erosion
Various erosion processes(sheet, rill, gully erosion, streambank erosion….) are spread onboth catchments.
Taking into consideration theshort distance from thereservoir, a great portion oferosive material produced fromthe catchment achieve to thereservoir.
Examples of gully erosion in the study area
Identification of runoff-generating plots and dischargecontributing areas by forest site
This delineation is donefollowing the approach givenby Schueler.
Taking into considerationthat gley soils are spread inthe valley in the study areaand out of the forestmanagement area, the rightside of the logical tree isexcluded.
Where:DSSF – Deep Sub Surface Flow - High infiltration rate due to macroporous andpermeable soil matrix. Lateral flow within a weathered layer above.
HOF – Hofman overlay flow - Susceptibility for surface sealing due to few macropores and a low permeable soil matrix.
SOF -Water saturation by infiltration into permeable soil layers above an impermeable layer
Water holding capacity
The type of runoff process can be changed ina case of saturation.Soil saturation depends on; (i) percentage ofsoil moisture, (ii) water holding capacity and(iii) intensity of the precipitation.
Soil texture and organic matter are the keycomponents that determine soil waterholding capacity, for instance:-silt and clay soils, have a larger surface areaand a higher water holding capacity.- sandy soils have large particle sizes whichresult in smaller surface area. The waterholding capacity for sandy lands is low.
Discharge accelerating linear structures - Forest roads
• Within the study area, there is a local asphaltroad that connect villages Bushkash and Baz androad goes almost along the boundary of thecatchment 1 in the southern part. From Bazicontinue slightly along the watershed boundaryand then curve out of the study area in directionto the village Drita or further.
• Other roads are unpaved.
• Тhe underlying premise is that forest roadspromote rapid runoff. This negative effect can bediminuished with special construction methodsand precautionary measures.
A decision tree with “yes/no”- key questions were developed to evaluate runoff fromforest roads (BACKES 2005).
• Question 1: If a road seals the forest soil surface then is causesHortonian overland flow (HOF).
• Answer 1: If the road and accompanying ditches enable the surfacewater to be widely diffused back into the forest, the runoff isestimated to be comparable to that of the surrounding forest sites.
• Question 2: Does the road has a humus layer, branch-woodreinforcement, or vegetation cover ?
• Answer 2: Our investigations showed that these can improve therunoff reaction (BACKES 2005). Surface water on bare dirt roadsbecomes overland flow (SOF, HOF) and the steeper the road thefaster the runoff.
Decision tree to derive the runoff from forest roads
FOREST MANAGEMENTSome data on forest resources
The total forest area is 4.548 ha divided into three management forms respectively: high forest(1.516,5 ha), coppice (2.659 ha) and shrubs (325 ha).
Due to human intervention and conventional management, the forest stands are young with mixedorigin (seed and sprouts). For these reasons, the forest resources are nearly natural and mostlyregenerated by sprouts.
The forest stands in the study area have protection and recreation function, because are locatedclose to the Ulza reservoir, and might be used as buffer zone.
These forest stands have been used traditionally to provide firewood and fodder for livestock.
Common practices of forestry in Ulza watershed
The main forest activities planned in management plan for the study area are:
