전세계적으로 인구가 증가하면서 물이 부족하게 되고, 물사용량이 많은 농·축산물 분야를 중심으로 물 사용량을 저감하기 위해 물발자국 연구가 시작되었으며, 중요한 이슈가 되고 있다. 본 연구는 물발자국을 산정하기 위해 국내 수자원의 특성을 반영한 특성화인자를 개발하고, 국가의 기반이 되는 사회기반시설 중 주요시설인 고속국도와 고속철도에 대해 물발자국을 산정하는 데 있다.
본 연구에서 국내 수자원의 특성을 반영하여 개발한 특성화인자는 지하수와 지표수에 대해 한강유역, 낙동강유역, 금강유역, 섬진강유역, 영산강유역, 제주도의 6개 유역별로 구분된다. 각 유역별로 지하수의 특성화인자는 0.073, 0.127, 0.118, 0.045, 0.154, 0.170이며, 지표수의 특성화인자는 각각 0.074, 0.115, 0.256, 0.142, 0.235, 0.245이다.
물발자국은 고속국도와 고속철도를 대상으로 개발한 물발자국 영향평가방법론(Kim방법)과 기존의 물발자국 영향평가방법론으로 Boulay방법론(Boulay방법)과 Ecoinvent를 이용한 국내 환경부 방법론(환경부A방법)과 국내 LCI DB를 이용한 환경부 방법론(환경부B방법)을 적용하여 산정되었다.
물발자국의 산정범위는 고속국도의 경우, 시설물의 자재생산단계, 시공단계, 운영 및 유지보수단계이며, 고속철도는 데이터 수집이 어려운 유지보수단계를 제외한 자재 생산단계, 시공단계, 운영단계이다.
Boulay방법, 환경부A방법, 환경부B방법, Kim방법에 의하면 고속국도 1 ㎞ 기준의 물발자국은 각각 58,804 ㎥ H2Oeq., 42,036 ㎥ H2Oeq., 27,461 ㎥ H2Oeq., 15,313 ㎥ H2Oeq.로, 고속철도 1 ㎞ 기준의 물발자국은 각각 490,551 ㎥ H2Oeq., 307,548 ㎥ H2Oeq., 55,988 ㎥ H2Oeq., 116,631 ㎥ H2Oeq.로 나타났다. 이러한 원인은 사용량이 많은 물질과 물질의 물소비계수로 인한 차이이다. 주요물질이 10% 저감 시, 민감도 분석결과는 고속국도가 1.87%∼7%, 고속철도가 6.67%∼9%로 저감되는 것으로 나타났다.
국내 도로에 대해 장래 예측 물발자국을 살펴보면, 2020년은 국내 고속국도가 물수요량의 0.04%∼0.17%, 도로는 0.22%∼0.86%로 나타났으며, 국내 도로의 경우, Boulay방법이 Kim방법보다 3.9배 높게 나타났다. 2025년은 국내 고속국도가 물수요량의 0.01%∼0.05%, 국내 도로는 0.10%∼0.74%로 나타났으며, 국내 도로의 경우 환경부B방법이 Kim방법의 7.5배 높게 나타났다. 2020년과 2025년의 차이는 2020년은 개통되는 국내 고속국도와 도로의 연평균 연장이 2025년에 비해 길기 때문이다. 주요물질이 10% 저감 시, 2020년의 민감도 분석 결과는 국내 고속국도가 1.91%∼7%, 국내 도로가 0.57%∼5%로, 2025년은 국내 고속국도와 도로 모두 9.68%∼9.90%로 저감되는 것으로 나타났다.
국내 철도에 대해 장래 예측 물발자국을 살펴보면, 2020년의 경우, 국내 고속철도는 물수요량의 0.01%∼0.06%, 국내 철도는 0.10%∼1.00%로 나타났으며, 자재생산단계에서의 물발자국이 높기 때문에, Boulay방법이 환경부B방법에 비해 8배, 9배가 높게 나타났다. 2026년의 경우, 국내 고속철도는 물수요량의 0.01%∼0.06%, 국내 철도는 0.05%∼0.33%로 나타났으며, 국내 철도의 경우 Boulay방법이 환경부B방법에 비해 8배, 11배가 높게 나타났다. 주요물질이 10% 저감 시, 2020년의 민감도 분석결과는 국내 고속철도가 6.37%∼9.6%, 국내 철도가 9.2%∼11.9%, 2026년은 국내 고속철도가 8.8%∼9.8%, 국내 철도가 10.6%∼11.7%로 저감되는 것으로 나타났다.
마지막으로 본 연구에서 제안한 LCI Database와 물발자국 영향평가방법론은 인프라시설에 적용될 필요가 있다. 예를 들면, 댐, 공항, 항만 등에 대한 물발자국을 산정하고, 예측하여 물수요량을 파악하고, 전과정비용평가 (LCC) 및 전과정평가(LCA)를 통해 비용과 환경영향을 파악하는 동시에 물발자국을 포함하여 물소비를 저감하기 위한 정책으로 반영될 필요가 있다.

As the population increases in the world, the water consumption is increasing and the availability of water resource is likely to decrease. Therefore, to manage and reduce water consumption, the study on water footprint was started mainly focused on the agriculture and livestock products which are high water usage sectors.
The aim of this study is to develop the characterization factor and calculate the water footprint in expressway and high-speed railway. With these study purposes, the characterization factors were developed in 6 classified watersheds which are Han river, Nakdong river, Gum river, Seumjin river, Youngsan river and Jejudo about surface water and ground water. considered characteristic of domestic water resources. As a result, the characterization factors of ground water in each watershed are 0.073, 0.127, 0.118, 0.045, 0.154 and 0.170. The characterization factors of surface water in each watershed are 0.074, 0.115, 0.256, 0.142, 0.235 and 0.245.
Using the developed characterization factors and methodology developed on this study (Kim''s method or Kim), Boulay''s methodology (Boulay''s method or Boulay) and MOE''s methodology using Ecoinvent(MOE''s A) and domestic LCI database(MOE''s B) as impact assessment of water footprint, the water footprint was calculated in expressway and high-speed railway.
The system boundary of water footprint was included the stage of raw material process and production, construction, operation and maintenance of expressway. In case of the high-speed railway system, the stage of material production, construction and operation were considered, however the maintenance stage was excluded with difficulty of data collection.
The water footprint on the basis of 1 ㎞ of expressway by Boulay, MOE''s A, MOE''s B and Kim is 58,804 ㎥ H2Oeq., 42,036 ㎥ H2Oeq., 27,461 ㎥ H2Oeq., 15,313 ㎥ H2Oeq. and the water footprint of high-speed railway is 490,551 ㎥ H2Oeq., 307,548 ㎥ H2Oeq., 55,988 ㎥ H2Oeq., 116,631 ㎥ H2Oeq.. because of amount of materials and differency of water consumption coefficient. The result of sensitivity analysis by reducing 10% of key issue is expressed to be reduced from 1.87% to 7% in expressway and 6.67% to 9% in high-speed railway.
The future prediction of water footprint in 2020 was from 0.04% to 0.17% of total water demand in domestic expressway and from 0.22% to 0.86% in domestic road. The water footprint by Boulay''s method was 3.9 times higher than by Kim''s method. The change of water footprint by 2025 was from 0.01% to 0.05% in domestic expressway and from 0.10% to 0.74% in domestic road. The water footprint by MOE''s B in domestic road was 7.5 times higher than by Kim''s. The difference between 2020 and 2025 is because the annual average increased distance to 2020 is relatively longer than to 2025. The result of sensitivity analysis in 2020 about domestic expressway by reducing 10% of key issue was expressed from 1.91% to 7% and about domestic road from 1.91% to 7% and in 2025 from 9.68% to 9.90% about both of them.
The predicted water footprint in 2020 was from 0.01% to 0.06% of total water demand in domestic high-speed railway and from 0.10% to 1.00% in domestic railway. The water footprint by Boulay was 8 times higher than by MOE''s B in domestic high-speed railway and 9 times in domestic railway. One of 2026 was from 0.01% to 0.06% in domestic high-speed railway and from 0.05% to 0.33% in domestic railway. The water footprint by Boulay was 8 times higher than by MOE''s B in domestic high-speed railway and 11 times in domestic railway. Difference of 2020 and 2025 is because of water footprint in the material production and construction. Result of sensitivity analysis in 2020 about domestic high-speed railway by reducing 10% of key issue expressed to be reduced from 6.37% to 9.6% and about domestic railway from 9.2% to 11.9%. It expressed to be reduced from 8.8% to 9.8% about domestic high-speed railway and from 10.6% to 11.7% about domestic railway in 2026.
Finally, LCI DB and Korea''s typical impact assessment for water footprint proposed on this study, is necessary to be applied. Thus the water footprint in other infrastructure system such as damn, airport, harbour and so on needs to be carried out and water footprint such as cost by life cycle costing (LCC) and environmental impact by life cycle assessment (LCA) need to be reflected to national policy to reduce water consumption.