우리나라 농업 물리탐사: 적용 사례와 향후 과제

Agricultural Geophysics in South Korea: Case Histories and Future Advancements

Abstract

우리나라 농업부문에 최초로 적용된 물리탐사 기술은 전기비저항 수직탐사로, 1970년대 농업용 지하수 탐지 목적으로 적용되기 시작하였다. 농업활동이 다변화된 1990년대 이후에는 기존의 전기비저항 탐사 이외에 유도 전자기 탐사, 자연전위 탐사 등을 이용하여 대규모 간척지 염분 집적 등 토양 특성 파악, 농업현장을 포함한 지하수 공급의 최말단부인 해안지역 소유역의 해수침투 범위 탐지, 저수지 및 방조제 안전진단을 위한 물리탐사, 과잉양수에 의한 지반침하 탐지, 쓰레기 매립장 또는 가축 매몰지로부터 발생되는 침출수 누출 범위 추적 등 다양한 분야로 확대되어 활용되고 있다. 본 원고에서는 이러한 농업부문에서의 물리탐사 기술 적용 사례들을 소개하고, 이를 기반으로 미래 농업에서 추구하는 정밀농업 현장에 필요한 물리탐사 기술의 발전 방안을 제시하였다.

The first geophysical technique applied to the agricultural sector in Korea was electrical resistivity sounding and conducted in purpose of groundwater exploitation in the 1970s. According to the diversity of agricultural activities since the 1990s, various geophysical methods including electrical resistivity, electromagnetic induction, and self-potential method were applied to several agricultural fields such as soil characterization with saline concentration in vast reclaimed area, delineation of seawater intrusion regions in costal aquifer, safety inspection of embankment dikes with leakage problem, detection of ground subsidence from overpumping and tracing of groundwater aquifer contamination by leachate from livestock mortality burial or waste burial site. This paper introduces representative geophysical techniques that have been utilized in various agricultural fields and suggests several ways to develop the geophysical methods required for the precision agriculture field in the near future based on the past achievements.

Fig. 1. Equi-potential lines during pumping test at test site. (a) 10 min, (b) 60 min, (c) 120 min (pumping stop), and (d) 150 min (Song and Yong, 2003).

Fig. 2. Comparing result between observed data and calculated data by 2-D SP forward modeling for reservoir dike with the pattern of leakage due to the composite effects of landslide and distortion of the dike (Song et al., 2002a).

Fig. 3. Apparent resistivity profiles from vertical electric sounding at three points over a year (Song et al., 2003a).

Fig. 4. Flow chart for sea dike maintenance using geophysical methods (EM: small-loop electromagnetic survey, ER: electrical resistivity survey, MASW: multichannel analysis of surface wave survey, SP: self-potential survey) (Yong et al., 2013).

Fig. 5. Contour maps of apparent conductivity drawn by semivariogram analysis. (a) 20,010 Hz; (b) 14,610 Hz; (c) 10,350 Hz; (d) 6,810 Hz; (e) 4,650 Hz; and (f) 3,150 Hz (Song, 2006).

Fig. 6. Correlation of conductivities obtained from electrical resistivity tomography method and water contents by soil analysis (Yong and Song, 2004).

Fig. 8. Evaluation of conceptual model using the results of settlement at each extensometer points (Song et al., 2004).

Fig. 9. 1D Inversion results of small-loop EM data with varying depths to the brackish water reservoir bottom, (a) 1 m and (b) 2 m, respectively (Song et al., 2011c).

Fig. 7. (a) 3D resistivity structures and (b) a schematic diagram of leachate flow superimposed on the iso-surface map of 30 ohm-m, respectively. Arrows indicate the expected direction of leachate flow (Song et al., 2015).

Table 1. Potential geophysical survey methods associated with hydrogeological survey for agricultural application.