울산시의주요생활용수공급댐인사연댐상류수몰지역내에국보285호인반구대암각화가위치하고있다. 표고53～57m에 위치한 암각화 보존을 위한 여러 가지 방안 중, 사연댐 수위를 60m에서 52m로 낮추어 물 밖으로 끄집어내는 안이주로검토되어왔다. 댐의수위를인위적으로조절하는경우저수량및용수공급량감소와더불어부영양화로인해수질이나빠지게된다. 본연구에서는사연댐수위조절에따른수질악화로댐의기능상실과수질변화로인해예상되는여러가지문제점을검토하였다. Vollenweider모델과CSTR (Continuous Stirred Tank Reactor) 모델을이용하여수위조절시변화가예측되는대표적인수질지표인BOD및COD그리고조류성장의주원인이되는총인과총질소의농도변화를분석하였다.그 결과 사연댐의 수위를 60 m에서 52 m로 조절하는 경우, COD의 농도는 약간 낮아지지만 총질소와 총인은 약 130%이상농도가증가되는것으로나타났다. 이러한변화는심각한조류문제를일으킬수있으며, 사연댐의수질관리를영양염류의 농도를 대상으로 하는 경우 수질이 악화되는 것으로 나타났다.

The Bangudae Petroglyphs, national treasure No. 285 is located within submerged upper districts of Sayeon dam supplying the main residential water in Ulsan. Of the many ways for the reservation of Petroglyphs located the altitude at 53～57 m, the plan that we take it out of the water lowering the water level from 60 m to 52 m has been examined mainly in case of controlling artificially the water level of the dam. In this paper, we examined expected problems from the loss of dam function and the change of water quality from water deterioration caused by the water level control of the Sayeon dam. Using the model of Vollen- weider and CSTR (Continuous Stirred Tank Reactor), we analyzed the density change of BOD and COD, representative water quality index and the TP and TN, the main reason of algae growth. The result showed that the density of COD lowered a little but the density of TP and TN went up over 130% when control- ling the water level from 60 m to 52 m. These changes cause a serious algae problem and if doing the water quality management as the density of TN and TP, the water quality would become worse. Water storage and supply residential water decreases, and the water quality becomes worse because of eutrophic state.

• 이상현(Senior researcher, Ulsan Development Institute Environment & Safety Divison,) | Lee, Sang Hyeon
• 조홍제(Professor, Department of Civil & Environmental Engrg., Ulsan Univ.) | Cho, Hong Je Corresponding Author