This paper presents a procedure to derive historical-annual and historical-monthly flow duration curves (FDC) that are monotonic and continuous for agricultural, unregulated, ungauged sites. The authors explore the performance and the regional dependence of four different regression models for the estimation of daily flow quantiles (QpQp), with probabilities of exceedance (pp) ranging from 0.01 to 0.99.

Perez, G., R. Mantilla, and W.F. Krajewski, Estimating annual and monthly scale-invariant flow duration curves for the State of Iowa, Journal of Hydrologic Engineering,23(12): 05018021, 2018.