Sivas 4 September Dam

Sivas 4 Eylül Dam, located in the Sivas province of Türkiye, is a water source constructed for the purpose of drinking water supply. Situated on the Mısmıl River and built between 1996 and 2002, this dam meets a significant portion of Sivas city’s drinking water demand. The dam’s total storage capacity is determined as 85 hm³, with an active volume of 80.55 hm³.

Sivas 4 September Dam - Photo: Halife Yalçınkaya/AA

Physical and Technical Characteristics

Location: Sivas Province, Mısmıl River

Construction Years: 1996–2002

Dam Type: Zoned earthfill

Watershed Area: 236.8 km²

Height from Thalweg: 60 metres

Height from Foundation: 65 metres

Embankment Fill Volume: 4,185,952 m³

Total Storage Capacity: 85 hm³

Active Storage Capacity: 80.55 hm³

Maximum Water Elevation: 1393.70 metres

Minimum Water Elevation: 1355 metres

Drinking Water Supply and Treatment Process

Surface water supplied by the dam is treated at the Sivas Municipality Drinking Water Treatment Plant before being fed into the distribution network. The treatment processes applied at the plant are as follows:

1. Coagulation and Flocculation: Water purification is achieved using potassium permanganate (KMnO₄), ferric chloride (FeCl₃), and anionic polyelectrolyte as coagulants.

2. Filtration and Disinfection: Chemical filtration processes are employed to remove contaminants such as manganese from the water.

3. Ozonation: Ozone units commissioned between 2018 and 2021 enhance the disinfection of the water.

Hydrological and Water Quality Characteristics

• Annual Water Supply Capacity: 33 hm³
• • Hardness Value: Water from Tavra Stream: 32 FH
  • Water from 4 Eylül Dam: 16 FH.

• Manganese Concentration: Manganese levels increase particularly during autumn months. In October 2010, manganese concentration was measured at 0.553 mg/L.
• • Manganese Removal Efficiency:
  • Using KMnO₄ alone: 94.7%
  • Using KMnO₄ + FeCl₃ + anionic polyelectrolyte: 96.3%
  • Under field conditions applying laboratory-determined optimal conditions: 53.4%

Conveyance and Distribution System

Water from 4 Eylül Dam is transferred to the Reservoir and Factory Reservoir located at mid and lower elevations of the city. A pumping line is required to supply water to higher elevations. Therefore, a 52-kilometre transmission line project has been completed to transfer 84.2 million m³ of water annually from Pusat Dam to 4 Eylül Dam.

Ecological and Environmental Impacts

The dam catchment area is an important region for water resource protection. However;

Pollution Risk: Waste water control must be ensured due to settlements in certain villages within the dam basin.

Climate Change and Water Resources: Global warming and declining rainfall rates are causing reductions in water levels.

Impact of Agricultural Activities: Substances entering the dam from tributaries negatively affect water quality during rainy periods.

Importance to Sivas and Future Plans

In addition to serving as Sivas’s primary drinking water source, the 4 Eylül Dam is supported by various projects aimed at ensuring future water security. Future plans include:

Pumping Station and Conveyance Line Project: Water from the dam will be delivered to higher elevations.

Pusat Özen Dam Connection: An annual supplement of 84.2 million m³ of water will be provided to 4 Eylül Dam.

Water Conservation and Leak Prevention Efforts: The loss-leakage rate has been reduced from 40% to 30%, with further reduction targeted.

Alternative Water Sources: Research continues on preserving existing water sources and ensuring sustainable use of groundwater.