1. MEASURING V.S MODELING SEDIMENT, CASE STUDY: KALIMANCI RESERVOIR
Ivan MINCEV
“Ss. Cyril and Methodius” University in Skopje, Forestry faculty, 16-ta Makedonska brigada No.1, 1000 Skopje, R. Macedonia,

2. EPM method (Gavrilvic) is the most widely used method for modeling erosion in ex-Yu countries
The methodology was validated with deposited sediment in existing reservoirs
EPM shows where is the sediment generated but it does not show the distribution of the deposited sediment in the catchment
Employing river bed hydraulic modeling of the sediment (HEC- RAS) to pinpoint the deposition patterns
Rationale

3. The aim of this paper is to show the difference between measuring sediment in the reservoir “Kalimanci” and estimating the sediment which is about to enter in the reservoir by using established modeling schemes. The separate objectives are: (1) to measure the deposed sediment in the reservoir and using the previous measurements to estimate the rate of filling up the reservoir with sediment, (2) to estimate the annual transported sediment in the reservoir using the EPM methodology, and (3) to estimate the transport of the sediment in the river Bregalnica up to the reservoir using hydraulic modeling employed in HEC-RAS and also to estimate how much of the sediment in the main river bed is deposited in the reservoir.
Aim and objectives

4. Study area - Catchment area of ​​the reservoir Kalimanci (1,135.3 km2)
Total storage 127x106m3
Study area - Catchment area of ​​the reservoir Kalimanci (1,135.3 km2)

5. Bathymetric measurements of the “Kalimanci” reservoir
Echo-sounder GPSMAP 421s
Bathymetric measurements of the “Kalimanci” reservoir

7. Between two measurements Cumulative Annually
No.
Year
Between two measurements
Cumulative
Annually m3
m3/year
1969 / 1
1971
1,661,225
830,612.5 2
1972
258,075
1,919,300
258,075.0 3
1973
147,625
2,066,925
147,625.0 4
1975
2,210,590
4,129,890
736,863.3 5
1977
1,046,775
5,176,565
523,387.5 6
1978
323,225
5,499,790
323,225.0 7
1980
1,233,190
6,732,908
616,595.0 8
1984
749,900
7,482,880
187,475.0 9
1985
406,010
7,888,890
406,010.0 10
1988 11
1991
1,514,690
9,403,580
252,448.3 12
1997
2,305,308
11,708,888
384,218.0
No.
Year
Between two measurements
Cumulative
Annually m3
m3/year 12
1997 ,0 13
2013 ,5

8. From the figure there can be distinguished two separate periods and In the first period the annual sedimentation of the reservoir is 467,686 m3/year and in the second the sedimentation is decreased to 214,325 m3/year.

9. Modeling transported sediment in the reservoir “Kalimanci” with the Erosion Potential Method (EPM)

10. All analyses were done on subcatchment level
Subcatchment delineation
All analyses were done on subcatchment level

11. 𝑿𝒂 Reclassification of vector topographic maps (Land Cover)
Reclassification of LPIS
Union of the two datasets
Buffer of stream layer (5-20 m)
Without measures 1,0
Built channels, check dams, other 0,7

12. Xa

13. The EPM was used to calculate the total load of the sediment in the reservoir. The average amount of transported sediment or how much of the annual produced sediment is deposited in the reservoir was calculated as the sum of average transported sediment of all the tributaries of the reservoir together with the immediate catchment of the reservoir. This means that the river Bregalnica was taken as a separate catchment. The amount of transported sediment in the reservoir “Kalimanci” was calculated on 277,393 m3/year. If this value is compared with the measured 214,325 m3/year and depreciated with the compaction of the sediment in the reservoir it can be said that these values are very close.

14. Modeling the transport of the sediment in the river Bregalnica up to the reservoir “Kalimanci” using hydraulic modeling employed in HEC-RAS

15. HEC-RAS HEC-GEO-RAS
One-dimensional model
Pfofiles 1 km
DТM 5m
Water discharge two gauging station: Berovo and Ochipale
Sediment input: annual transported sediment

17. Deposition zones
According calculations in HEC- RAS annualy in the reservoir are deposited m3 sediment. This amount is close with the values of the calculated values with EPM ( m3)

18. There can be distinguished three general zones of accumulation of sediment. If the profiles of accumulation are spatially transferred on the map it can be seen that accumulation of the sediment is in the larger valleys: Machevo – Mitrashinci, Razlovci and Trabotivishte - Delchevo. Almost 75% of the input sediment in the river Bregalnica is deposited in the valleys. Delcevsko pole is the largest deposition pool with 40% of the share od the sediment.

19. From the given results it can be conferred that measuring and modeling sediment is not the same. The existing models which estimate sediment transport and deposition give close approximation of the state of the environment. Also it should be considered for what kind of purpose they were initially developed.
Most of the developed theory is not very recent. In order to be implemented with the advances of the new technologies it should be modified.
Conclusion

20. The reservoir was measured with bathymetric measurements and the latest sedimentation rate was estimated to 214,325 m3/year. The values of the EPM for the sediment transport to the reservoir was estimated to be 277,393 m3/year. If the compaction of the sediment is considered then the modeling can be considered to be close to the measurements.
The EPM model for the catchment of Bregalnica was estimated to be 161,860 m3/year and on the other hand with the HEC-RAS model was estimated value of 152,231 m3/year.
The values of the three different approaches give similar result so it can be conferred that the methods are compatible, comparable and can be used in combination in order to use the different traits of the different approaches.
Conclusion

21. Thank you for your attention!!!