{H}ydrological parameter estimation for ungauged basin based on satellite altimeter data and discharge modeling. {A} simulation for the {C}aqueta {R}iver ({A}mazonian {B}asin, {C}olombia)

Abstract

{T}he main objective of this paper is to review the usefulness of altimetric data in ungauged or very poorly monitored basin. {I}t is shown that altimetric measurements can be combined with a single in-situ gauge to derive a reliable stage-discharge relationship upstream from the gauge. {T}he {C}aqueta {R}iver in the {C}olombian {A}mazon {B}asin was selected to simulate a poorly monitored basin. {T}hus it was possible to derive the stage-discharge relationship for 13 "virtual gauge stations' defined at river crossing with radar altimetric ground tracks. {S}tage measurements are derived from altimetric data following the methodology developed by {L}eon et al. (2006). {D}ischarge is modeled using {PROGUM} - a flow routing model based on the {M}uskingum {C}unge ({M}-{C}) approach considering a diffusion-cum-dynamic wave propagation ({L}eon et al., 2006) using a single gauge located downstream from the basin under study. {R}ating curve parameters at virtual stations are estimated by fitting with a power law the temporal series of water surface altitude derived from satellite measurements and the modelled discharges. {T}he methodology allows the ellipsoidal height of effective zero flow to be estimated. {T}his parameter is a good proxy of the mean water depth from which the bottom slope of the reaches can be computed. {V}alidation has been conducted by comparing the results with stages and discharges measured at five other gauges available on the {C}aqueta basin. {O}utflow errors range from 10% to 20% between the upper basin and the lower basin, respectively. {M}ean absolute differences less than 1.10 m between estimated equivalent water depth and measured water depth indicates the reliability of the proposed method. {F}inally, a 1.2×10 -4 mm -1 mean bottom slope has been obtained for the 730 km long reach of the {C}aqueta main stream considered.