Effectiveness of monitoring methods for soil leakage loss in karst regions

Abstract

Soil leakage loss is a special form of soil and water loss in karst areas and has been raising the research interest in the recent years. Owing to the invisibility and distinctiveness of soil leakage loss, how to effectively monitor it has become a tough problem. Through analyzing the existing methods, this study aims to assess their contributions to and deficiencies in understanding the law of soil leakage loss in karst areas. The results are produced as follows: (i) Simulation tests have given insights into the law and influencing factors of soil leakage loss under the double-layer karst structure, yet the small devices, the bedrock and soil transport, and the lack of vegetation, all impair their representativeness of the leakage loss realities of the vast karst area in the nature. (ii) 137Cs tracer is beneficial to quantitatively trace soil erosion in homogeneous soil and to confirm the existence of soil leakage loss phenomenon in heterogeneous soil of karst rocky desertification regions, whereas the exact amount of loss is hard to obtain in karst heterogeneous soil through this method. (iii) Cave dripping tracer has offered a more scientific way to reveal the law of soil leakage loss and estimate the loss amount, but the amount measured with this method has a low accuracy and reliability resulted from the unknown surface seepage area. (iv) Scratching and erosion pins, with the mathematical models, are practicable to calculate the soil and water leakage loss. Yet several obstacles low their efficiency and reliability: the errors in the total soil erosion and the transportation ratio, and the unreliability in short-time monitoring. The other methods, underground river sediment monitoring and underground water turbidity, are also applicable in monitoring the SLL in karst areas, but still confront some obstacles, including the uncertain uniqueness of the underground river, the unreasonable sediment transport ratio, and the turbidity meter limitation.