Relaciones agua-suelo-vegetación.-Assessing diffuse and concentrated recharge in average- and dry-rainfall year in a semiarid carbonate sloping aquifer, a preliminary report

Abstract

ABSTRACT The chloride mass balance (CMB) method was applied in the unsaturated zone to estimate potential recharge (RT) by rainfall in two small catchments of southern mid-to-high slope of Sierra de Gádor carbonate aquifer (SE Spain), in the average hydrological year 2003-04 and the unusually dry 2004-05. Unknown fractions of diffuse (RD) and concentrated recharge (RC) into RT were firstly evaluated to fit average and lower RT thresholds for modeling further longterm recharge. Daily rainfall and actual evapotranspiration (AET) from the Eddy Covariance (EC) technique provided yearly RT of 189 mm year-1 in 2003-04 and 8 mm year-1 in 2004-05. Difference on RT among CMB method and EC technique is ~5% in year 2003-04, increasing to ~25% in year 2004-05. RD from soil-moisture field data was 65 mm year-1 (~34% of RT) in 2003-04 and negligible in 2004-05. The use of complementary methods checks low RT rates and identifies RD and RC fractions mixing in the unsaturated zone before RT reaches the regional water-table top. The results can explain long-term variations on groundwater storage and hydrochemistry and validate lower RT ~ RC yearly rates from the EC technique.