Effects of agricultural land use on water chemistry of mire pools in the Ishikari Peatland, northern Japan

Abstract

Concomitant with farmland development in the Ishikari Peatland of northern Japan, deterioration of water chemistry has become increasingly evident at mire pools there. Using spatial analysis methods with a geographic information system and a statistical methodology, this study examined the effects of agricultural land use on the pool water chemistry. A water chemistry survey of several pools showed that nitrogen, phosphorus, and suspended-solid concentrations were remarkably higher than those in pools that had been undisturbed or less-disturbed by land-use development. Principal component analysis (PCA) was conducted to summarize water chemistry variables. Correlation analysis was conducted between the principal component (PC) scores and land-use variables to clarify land-use effects. Results of the PCA showed that the water chemistry variances were accounted for by the first two PCs: PC1 included farmland subsurface drainage containing nitrogen, specifically nitrate, and mineral ions; PC2 included farmland surface drainage containing soil particles and ammonium nitrogen. These PC scores were also affected by the number of inflow ditches and the total area of farmland located within the drainage catchment of inflow ditches leading to the pools. Results suggest that farmland subsurface and surface drainage water flowing into the pools degraded the water chemistry. The extent of the effects of drainage water depended on agricultural practices such as fertilizer application and paddy-field puddling (i.e., mechanical homogenization of water-saturated soil).Accordingly, water chemistry of the study pools was affected by agricultural practices and by the amount of farmland in the drainage basin, engendering eutrophication, and the deterioration of water chemistry. Therefore, preservation of water chemistry necessitates changes in agricultural practices, such as improving fertilizer application methods, along with measures related to land-use planning such as changing the drainage ditches' flow direction.

Hydrochemical zoning of valley peatlands as a result of water supply conditions - examples from Poland.

“…The second distinguished pair of ions, Na + and Ca 2+ , is very frequently interpreted in PCA of peat waters, together with other macro ions, as evidence of groundwater supply to peatlands (Blancher & McNicol 1987, Kizuka et al 2008, Stelmaszczyk et al 2009. Traces of penetration of KR by groundwaters are found in the depth distribution of PC2 values.…”

Geomorphic legacy controls macrophyte distribution within and across disconnected floodplain lakes

“…Marsh lakes occur in relatively downstream areas and have been in the same locations as far back as documented by existing records (aerial photographs and cartographic maps; oldest available 1917). Lakes are increasingly subjected to inputs of irrigation water drained from rice paddies, and deterioration of water quality has been reported (Kizuka et al, 2008). Natural lakes exist in relatively upstream areas.…”

“…However, most of the lakes have overland hydrological connections to the main channel via waterways with floodgates that are embedded in the dykes; these are shut only during large floods to prevent internal flooding. Lakes are increasingly subjected to inputs of irrigation water drained from rice paddies, and deterioration of water quality has been reported (Kizuka et al, 2008). We selected nine natural lakes, eight marsh lakes and five artificial lakes for the study; some lakes in the area were excluded from the survey because of obvious modifications of bottom bedforms (via past dredging) or water withdrawals during non-irrigation periods in winter.…”

Development of unmanned airboat for water-quality mapping

“…Therefore, many small lakes in Japan do not meet waterquality standards. It has been reported that lakes surrounded by farming areas, in particular, are polluted (T. Kizuka, Yamada, Yazawa, & Chung, 2008).…”