Gage Download By State

 public void DownloadStationsByState(string[] stateCodes, string localFilePath, StationFields stationFields = null)
        {
            this.localFilePath = localFilePath;
            DownloadedStations = new List<Station>();
            List<string> columnNames = stationFields == null ? StationFields.DefaultStationFields : stationFields;

            string url =
                "http://nwis.waterdata.usgs.gov/nwis/peak?" +
                string.Join("&", stateCodes.Select(stateCode => "state_cd=" + stateCode).ToArray()) +  // e.g. state_cd=va&state_cd=wa
                "&coordinate_format=decimal_degrees" +
                "&sort_key=site_no&group_key=NONE&format=sitefile_output" +
                "&sitefile_output_format=rdb" + // rdb = plain text in CSV

                // Column names
                string.Concat(columnNames.Select(field => "&column_name=" + field).ToArray()) +

                "&set_logscale_y=1&date_format=YYYY-MM-DD&rdb_compression=file&hn2_compression=file" +
                "&list_of_search_criteria=lat_long_bounding_box";

           DownloadStations(url, localFilePath);
        }

        private void DownloadStations(string url, string localFilePath)
        {
            webClient = new WebClient();
            webClient.DownloadFileCompleted -= WebClientOnStationDownloadCompleted;
            webClient.DownloadFileCompleted += WebClientOnStationDownloadCompleted;

            IsWebClientCancelled = false;
            IsWebClientBusy = true;

            webClient.DownloadFileAsync(new Uri(url), localFilePath);

        }