Prevention of soil water erosion and ensuring runoff quality (InVEST Sediment Delivery Ratio)
Two ecosystem services – 1) prevention of soil water erosion and 2) ensuring runoff quality – were estimated and mapped using InVEST Sediment Delivery Ratio model. The InVEST SDR model focuses only on overland erosion. Outputs from the model include the sediment load delivered to the stream at an annual time scale, as well as the amount of sediment eroded in the catchment and retained by vegetation and topographic features. The main indicator of the ES of prevention of soil erosion is avoided erosion, and the main indicator of the ES of ensuring runoff quality is avoided sediment export to streams.
The main results of ES modeling and mapping
InVEST model outputs are proxy variables that should be interpreted in relative terms, rather than physical quantities. Nevertheless, the identified values are useful for analyzing the spatial distribution of services across the country’s territory and their balance with indicators of service utilization by the population and the economy.
This section presents preliminary results of testing models for assessing and mapping ecosystem services. In the future, if a decision is made to use these models, they should be calibrated using hydrological measurements made in Armenia.
The methodology and results will be described in detail in a forthcoming publication.
1. ES evaluation and mapping in physical indicators
In 2023, total avoided erosion was estimated as 140 million tons, and total avoided sediment export to streams was estimated as 13 million tons.
Land cover 2023
Avoided erosion, tons/pixel/year Avoided export, tons/pixel/year 
For details see maps in the section “Sediment Delivery Ratio – Basic scenario 2023”
The highest rates of avoided erosion and sediment export per ha were found for watersheds Aghstev, Vorotan, and Debed and the corresponding marzes Tavush, Syunik, and Lori. The lowest values were found for watersheds Metsamor and Akhuryan and for the marz Armavir. This pattern, in general, is also evident for the total avoided erosion and sediment transport.
ES indicators in watersheds and marzes, 2023
| Total avoided erosion 2023, Mt/year | Total avoided sediment export 2023, Mt/year | Avoided erosion 2023, mean, t/ha/year | Avoided sediment export 2023, mean, t/ha/year | ||
| Wtersheds | Aghstev | 28.9 | 1.7 | 93.5 | 5.5 |
| Akhuryan | 6.1 | 0.8 | 22.7 | 2.9 | |
| Arpa | 20.1 | 2.2 | 47.1 | 5.2 | |
| Debed | 27.6 | 2.2 | 72.3 | 5.9 | |
| Hrazdan | 18.6 | 2.0 | 32.3 | 3.5 | |
| Metsamor | 6.6 | 0.7 | 19.0 | 2.1 | |
| Vorotan | 32.6 | 3.4 | 74.8 | 7.8 | |
| Marzes | Aragatsotn | 6.6 | 0.7 | 25.2 | 2.7 |
| Ararat | 6.5 | 0.7 | 32.1 | 3.5 | |
| Armavir | 0.4 | 0.1 | 3.5 | 0.5 | |
| Gegharkunik | 14.9 | 1.6 | 38.8 | 4.2 | |
| Kotayk | 7.3 | 0.7 | 35.7 | 3.6 | |
| Lori | 26.9 | 2.1 | 73.6 | 5.9 | |
| Shirak | 6.6 | 0.8 | 25.3 | 3.2 | |
| Syunik | 32.6 | 3.4 | 74.8 | 7.8 | |
| Tavush | 25.7 | 1.4 | 96.8 | 5.4 | |
| Vayots Dzor | 12.9 | 1.4 | 57.7 | 6.4 | |
| Armenia | 140.4 | 13.0 |
The model estimates that vegetation prevents more than 90% of erosion in all watersheds and marzes (except for the Armavir Province) and more than 95% of sediment export everywhere.
Erosion on bare ground, tons/pixel/year Actual erosion in 2023, tons/pixel/year
For details see maps in the section “Sediment Delivery Ratio – Basic scenario 2023”
| Mean erosion on bare ground, t/ha/year | Mean current erosion 2023, t/ha/year | Mean avoided erosion 2023, t/ha/year | Total erosion on bare ground, Mt/year | Total current erosion, 2023, Mt/year | Total avoided erosion 2023, Mt/year | Share of avoided erosion, % | ||
| Watersheds | Vorotan | 78.8 | 4.0 | 75.0 | 34.3 | 1.7 | 32.6 | 94.9 |
| Metsamor | 20.3 | 1.3 | 19.0 | 7.1 | 0.5 | 6.6 | 93.6 | |
| Hrazdan | 34.3 | 1.9 | 32.3 | 19.8 | 1.1 | 18.6 | 94.3 | |
| Debed | 75.2 | 2.9 | 72.4 | 28.7 | 1.1 | 27.6 | 96.1 | |
| Arpa | 49.6 | 2.5 | 47.0 | 21.1 | 1.1 | 20.1 | 95.0 | |
| Akhuryan | 24.7 | 2.0 | 23.0 | 6.6 | 0.5 | 6.1 | 92.0 | |
| Aghstev | 96.0 | 2.5 | 93.5 | 29.7 | 0.8 | 28.9 | 97.4 | |
| Marzes | Aragatsotn | 26.8 | 1.6 | 25.2 | 7.1 | 0.4 | 6.6 | 93.9 |
| Ararat | 33.8 | 1.7 | 32.1 | 6.9 | 0.3 | 6.5 | 94.9 | |
| Armavir | 3.9 | 0.4 | 3.5 | 0.5 | 0.1 | 0.4 | 89.1 | |
| Gegharkunik | 41.1 | 2.3 | 38.8 | 15.8 | 0.9 | 14.9 | 94.4 | |
| Kotayk | 37.7 | 2.0 | 35.7 | 7.7 | 0.4 | 7.3 | 94.6 | |
| Lori | 76.5 | 2.9 | 73.6 | 28.0 | 1.1 | 26.9 | 96.2 | |
| Shirak | 27.4 | 2.1 | 25.3 | 7.1 | 0.5 | 6.6 | 92.3 | |
| Syunik | 78.8 | 4.0 | 74.8 | 34.3 | 1.7 | 32.6 | 94.9 | |
| Tavush | 99.2 | 2.4 | 96.8 | 26.4 | 0.6 | 25.7 | 97.6 | |
| Vayots Dzor | 60.8 | 3.1 | 57.7 | 13.6 | 0.7 | 12.9 | 95.0 |
Current erosion and current export are values with current land cover in 2023
| Mean current sediment export 2023, t/ha/year | Mean avoided sediment export 2023, t/ha/year | Total current sediment export 2023, Mt/year | Total avoided sediment export 2023, Mt/year | Share of avoided sediment export, %* | ||
| Watersheds | Aghstev | 0.2 | 5.5 | 0.0 | 1.7 | 97.3 |
| Akhuryan | 0.1 | 2.9 | 0.0 | 0.8 | 95.3 | |
| Arpa | 0.2 | 5.2 | 0.1 | 2.2 | 96.7 | |
| Debed | 0.2 | 5.9 | 0.1 | 2.2 | 96.7 | |
| Hrazdan | 0.1 | 3.5 | 0.1 | 2.0 | 96.4 | |
| Metsamor | 0.1 | 2.1 | 0.0 | 0.7 | 96.1 | |
| Vorotan | 0.3 | 7.8 | 0.1 | 3.4 | 96.2 | |
| Marzes | Aragatsotn | 0.1 | 2.7 | 0.0 | 0.7 | 96.2 |
| Ararat | 0.1 | 3.5 | 0.0 | 0.7 | 96.5 | |
| Armavir | 0.0 | 0.5 | 0.0 | 0.1 | 95.1 | |
| Gegharkunik | 0.1 | 4.2 | 0.1 | 1.6 | 96.6 | |
| Kotayk | 0.1 | 3.6 | 0.0 | 0.7 | 96.1 | |
| Lori | 0.2 | 5.9 | 0.1 | 2.1 | 97.0 | |
| Shirak | 0.1 | 3.2 | 0.0 | 0.8 | 96.2 | |
| Syunik | 0.3 | 7.8 | 0.1 | 3.4 | 96.6 | |
| Tavush | 0.2 | 5.4 | 0.0 | 1.4 | 97.2 | |
| Vayots Dzor | 0.2 | 6.4 | 0.0 | 1.4 | 96.6 |
Mt – million tons
Current export are values with current land cover in 2023
2. ES changes from 2017 to 2023
Changes in the landcover from 2017 to 2023 resulted in changes in avoided erosion and sediment export. These changes represent only tenths of a percent of ES volume, but can be important for tracking trends.
Changes from 2017 to 2023 (red indicates a decrease, blue indicates an increase.)
Changes in avoided erosion Changes in avoided sediment export 
For details see maps in the section “Sediment Delivery Ratio – Dynamics”
The average and total values of avoided erosion decreased in marzes Shirak, Syunik, Lori, Gegharkunik, and Aragatsotn. Consequently, current erosion and current sediment export as well as avoided sediment export increased in those marzes. The pattern of changes in remaining marses is opposite.
3. The degree of ES use and the degree of satisfaction of the need for it
This section is based on a comparison of estimates of avoided sediment export in streames by the SDR InVEST model and data on water consumption from ArmStat regional statistics. Taking into account water use in the marzes, the ES of ensuring runoff quality is most important in the Lori marz, where ecosystems prevent the export of 119 kg of sediment per 1 m3 of water use, and least in the Armavir marz, where this indicator is only 0.1 kg/year. 
The degree of satisfaction of the need for this ES everywhere exceeds 95%
| Sediment export per m3 of total water use, 2023, kg/m3/year | Avoided sediment export per m3 of total water use, 2023, kg/m3/year | Share of avoided sediment export per m3 of water use, % | |
| Aragatsotn | 0.1 | 3.1 | 96.2 |
| Ararat | 0.0 | 0.9 | 96.7 |
| Armavir | 0.0 | 0.1 | 95.4 |
| Gegharkunik | 1.1 | 29.1 | 96.5 |
| Kotayk | 0.2 | 4.4 | 96.3 |
| Lori | 4.0 | 119.1 | 96.8 |
| Shirak | 0.6 | 13.0 | 95.4 |
| Syunik | 1.7 | 42.6 | 96.3 |
| Tavush | 1.8 | 67.6 | 97.4 |
| Vayots Dzor | 2.0 | 59.5 | 96.7 |