DOI: 10.5061/dryad.np5hqc02x
title: Water quality and spatial parameters from the main channel of a 6th order stream collected with an uncrewed surface vehicle

description: Nitrate concentrations in streams and rivers in the midwestern United
 States are often elevated, reflecting the predominance of agriculture in
 the surrounding landscape. Recent advances in technology, including
 surface-water drones and more precise sensors, provide an opportunity to
 investigate nitrate dynamics with high spatial and temporal resolution. We
 deployed an aquatic drone, the AquaBOT, in a 6th-order, agriculturally
 influenced river to examine longitudinal patterns in water quality. Our
 goal was to measure the spatial and temporal heterogeneity in nitrate and
 nitrate-removal processes and determine the influence of tributary inputs
 on mainstem chemistry. We navigated the drone along a 12-km reach of the
 Des Moines River (Iowa, USA) nine times between June 2021 and August 2022.
 Across the deployments, mean nitrate concentration was positively related
 to discharge and was nearly two orders of magnitude higher in spring than
 summer. We observed contrasting patterns in mainstem nitrate, which
 decreased downstream during some runs (e.g., 3.1 to 2.7 mg N/L in June
 2021), demonstrating nitrate uptake along the reach, and remained constant
 on other dates. Similarly, tributaries to the Des Moines had varied
 influence on riverine nitrate, either increasing or decreasing nitrate
 concentrations depending on the tributary and date. Nitrate removal rates
 were spatially and temporally variable but showed some consistency at the
 sub-reach (2 km) scale, with two sub-reaches in particular often showing
 elevated rates of nitrate removal across dates. Our study reveals nuanced
 heterogeneity in nitrate dynamics of the Des Moines River despite the
 homogeneity of agricultural land cover in the watershed. 
description: This dataset was collected along a 12.4-km reach of the Des
 Moines River, a 6th-order river in Central Iowa, USA. The study reach,
 located ~50 km northwest of the city of Des Moines, Iowa, begins at the
 upstream site (UP) near Boone, Iowa at 42°02'13.6"N
 93°55'39.8"W and ends at the downstream site (DOWN) at
 41°57'59.0"N 93°53'47.0"W. A surface-water drone
 equipped with water-quality sensors (the “AquaBOT”) measured longitudinal
 patterns in water chemistry along the 12.4-km reach of the Des Moines
 River. Nine AquaBOT runs were carried out in the spring through fall
 across two years (2021, 2022)
description: # AquaBot Manuscript Supporting Data
 [https://doi.org/10.5061/dryad.np5hqc02x](https://doi.org/10.5061/dryad.np5hqc02x) ## Description of the data and file structure This dataset contains water quality parameters (Water temperature, specific conductivity, dissolved oxygen, and nitrate-N) from sensors attached to an aquatic uncrewed surface vehicle (drone) within the main channel of our study reach as well as distance down stream calculated from the drones GPS coordinates. Each tab contains these main channel parameters for one of the 9 sampling dates. These data are essential for understanding the longitudinal patterns in nitrate and conductivity detailed in our research paper.  ### Files and variables #### File: Mainstem\_AquaBOT\_Data\_Format.xlsx **Description:** Water quality parameters for each sampling date. Main channel values only. ##### Variables * TIMESTAMP: the date and time of each record. Each tab within the file is a separate date.  * Water_Temp_deg C: Water temperature in degrees Celsius * Sp_Cond_uS/cm: Specific conductivity in microsiemens per centimeter * ODO_%sat: Dissolved oxygen in percent saturation * ODO_mg/L: Dissolved oxygen in milligrams per liter * NO3-N_mg/L: Nitrate-N in milligrams per liter * distFromStart_m: Distance downstream within the main channel of the river from the starting point of sampling