The São Francisco river flow is regulated by a series of dams that work in cascade for hydro-power generation, maintaining the flow <1000 m³ s⁻¹ all year long. This caused the dampening of the flood peaks and perpetuated the salt intrusion, changing the function of the system as a material source to the coastal ocean. Here we present an assessment of the estuary salt intrusion, hydrodynamics, mixing processes, and the transport of scalars based on field observations. The mains goal is to evaluate its present role as a sink or source of materials to the adjacent sea. Three tidal surveys were carried out to gather data on the water level, cross-section discharge, current velocity and direction, salinity, temperature, concentration of suspended particulate matter (SPM), dissolved oxygen, and chlorophyll. Data were recorded from moored instrumentations in different locations, from boat-based sampling in a cross-section, and also in along-estuary surveys. The estuary shows a highly stratified salinity distribution, with the salt intrusion excursion of 7 km during the spring tide, reaching $\sim$11 km at high tide. The salt intrusion is laterally asymmetric, influenced by the system morphology. There is a strong tidal attenuation along the estuary, even though the flow regime is sub-critical (Richardson Number > 0.25). The estuary presented lateral variability of currents modulated by the tide, being horizontally sheared during spring tide and vertically sheared during neap. The transport of scalars was modulated by the tide, and the estuary exported SPM, dissolved oxygen, and chlorophyll both during neap (44.4, 12.9 and 3.6x10⁻³ kg s⁻¹, respectively) and spring tide (31.8, 7.4 and 2x10⁻³ kg s⁻¹), despite the severe flow regulation, meaning that the system still functions as a source of materials to the coastal sea.

圣弗朗西斯科河的水流由一系列大坝调节，这些大坝为水力发电而梯级工作，从而使水流保持<1000 m ³ s ^-1一整年。这导致洪峰的衰减，盐分的入侵持续存在，改变了该系统作为沿海海洋物质来源的功能。在这里，我们根据现场观察结果，对河口盐的入侵，流体动力学，混合过程以及标量的运输进行了评估。主要目标是评估其作为邻近海域的物质汇或来源的当前作用。进行了三次潮汐调查，以收集有关水位，横断面流量，流速和方向，盐度，温度，悬浮颗粒物（SPM）浓度，溶解氧和叶绿素的数据。数据是从不同位置的系泊仪器，横截面船上采样以及沿河口调查中记录的。$〜$涨潮时11公里。盐侵入在横向上是不对称的，受系统形态的影响。即使水流处于次临界状态，沿河口的潮汐衰减也很大（理查森数> 0.25）。河口呈现出由潮汐调制的电流的横向变化性，在春季潮汐时被水平剪切，在净潮时被垂直剪切。标量的输送是由潮（44.4，12.9和3.6x10调制，河口两个小潮期间导出的SPM，溶解氧，和叶绿素^-3千克小号^-1分别）和大潮（31.8，7.4和2×10 ^{- 3} kg s ^-1），尽管进行了严格的流量调节，这意味着该系统仍然充当着沿海海域的物质来源。