Relationship between increment of groundwater level at the beginning of irrigation period and paddy filed area in the Tedori River Alluvial Fan Area, Japan

Abstract

There are many paddy fields and large amounts of groundwater in the Tedori River Alluvial Fan in Ishikawa Prefecture, Japan. Water infiltration from paddy fields during irrigation may significantly contribute to groundwater recharge. Groundwater recharge is known to be one outcome of paddy farming, and in general is usually related to land use. However, a decreased area of paddy fields because of socioeconomic factors such as urbanization and increasing area of fallow fields, has possibly affected the groundwater environment. Evaluation of the quantitative effect of paddy fields on groundwater is necessary for groundwater conservation. This study examined the relationship between differences in the depth of groundwater from just before the irrigation period to just after the first irrigation of paddy fields (increments of groundwater levels) in observation wells and the area of paddy fields around each well. The paddy areas within circular buffer zones, which were delineated at 0.2 km intervals between 0.2 km and 2.0 km centered on each observation well, were calculated. A positive relationship was found between the rise in groundwater and the area of paddy field within different buffer zones at most wells. Additionally, in the middle or upper part of the fan, the effect of changes in the area of paddy fields surrounding the well on the groundwater level rise was greater than that on the lower part of the fan.

Seasonal Variations in Groundwater Level and Salinity in Coastal Plain of Eastern China Influenced by Climate

“…The groundwater level is a key parameter for evaluating spatial and temporal changes in groundwater environments [3]. The groundwater level is governed by various factors.…”

Multiple-indicator study of groundwater flow and chemistry and the impacts of river and paddy water on groundwater in the alluvial fan of the Tedori River, Japan

“…Iwasaki et al . () examined changes in groundwater level at the beginning of the irrigation period and showed that they are closely related to the areal extent of local paddy fields. They measured groundwater levels at 113 wells in December 1993, 87 wells in November 2009, and 86 wells in June 2010.…”

“…To maintain sustainable groundwater use and prevent groundwater contamination, it is important to understand the source and flow paths of groundwater in the fan. Large areas of the fan are covered by paddy fields (45% in 2009), so infiltration of irrigation water makes a considerable contribution to groundwater recharge (Matsuno et al, 2006;Iwasaki et al, 2013a). There are concerns about the impact of paddy farming on groundwater quality, for example, through the application of fertilizer and its indirect consequences such as cation exchange reactions between water, rock, and soil.…”

Examination of the water balance of irrigated paddy fields in SWAT 2009 using the curve number procedure and the pothole module

“…Therefore, the seepage from the pothole to the soil layers becomes zero on most days. Using the pothole module for paddy fields is problematic because the recharge of aquifers by the percolation of ponded water is a feature of the paddy hydrology (Iwasaki et al 2013). This problem does not occur for pothole landscapes.…”