River inputs are critical for studies of the coastal ecosystem. Specifically, the regional modeling community needs standardized data input for both streamflow and water quality. We used Mississippi as an example and examined the data to find it is generally consistent with the river inputs we have composed based on USGS measurements regarding river discharge, nutrient, and carbonate variables. My only suggestion is that currently, the data stopped in 2020, and I would encourage the authors to continuously extend the database in an up-to-date mode. 

The RC4USCoast package is a useful compilation of river carbonate chemistry and discharge data for coastal ocean modeling purposes. The manuscript is clearly written and the data quality is excelent based on the best avaialble USGS results. 

A few minor comments:

P3 L63-64, the expression is confusing, you really meant that using TA and pH to estimae DIC may overestimate the latter because of the inclusion of non-carbonate alkalinity. Actually non-carbonate alkalinity itself is not precise, borate isn't a part of carbonate alkalintiy as well. 

Throughout the text, please change carbon chemistry to carbonate chemistry, please be precise. 

Table 1, the variable DIC should have both measured (a small fraction) and calculated, need to be complete. 

P6 L116, DIC:Alk = 3.5 as cutoff for throwing out outliers, please explain. 

P9 L144, "Blackwater". it seems that there are more than one Blackwater Rivers in the US, please specify its location. In viewing the data, this is a very small tributary in Alabama to a another small river, not into the coast directly. Please reexamine the listed rivers and make sure they actually contribute to the coastal ocean. 

There are eight different pararmeters that can be interpreted as alkalinity more or less. For cases that these results do not agree (which occurs actually quite often), please explain how you merged the data.