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The groundwater balance for the city of Nagaoka, Japan is presented as a case study. At Nakaoka there are three interesting features: (a) in winter groundwater is ejected from pipes under the roads to melt freshly fallen snow, (b) the river is hydraulically in contact with the aquifers, (c) the water table has remained quasi-stationary for the last five years despite the vast pumping programme. The main sources of recharge are: the River Shinano, deep percolation from irrigated fields, snowmelt in spring, and rainfall throughout the year. The water table was monitored using observation data from about 200 wells; during the irrigation period in August there was an inflow of groundwater, but groundwater resources were depleted in winter and spring by pumping for the snow-melting scheme. The evaluation and estimation of the components of the groundwater balance are discussed; in particular methods of measuring deep percolation either directly or indirectly are examined.