*3.3. Data Collection*

*3.3. Data Collection*  The study was developed based on the guidelines of the United States Environmental Protection Agency (USEPA) Handbook for Developing Watershed Plans to Restore Our The study was developed based on the guidelines of the United States Environmental Protection Agency (USEPA) Handbook for Developing Watershed Plans to Restore Our Waters [36]. A summary of the data used in the study can be found in Table 1. NPS pollutant loads through sediment and runoff courses are highly related not only to land use/cover characteristics but also to topography [37–39]. This study integrates land cover data from the 2016 National Land Cover Database (NLCD) [40] with a spatial resolution of 30 m to determine relative contributions of NPS pollution in the north and central watersheds. The land cover type data identified as NPS pollution encompass urban and agricultural areas only. Each watershed was treated individually to characterize the type of land cover in the area. The NPS pollutants identified within the watersheds were cultivated crops areas and urbanized areas and South Texas large ranches (STLR), species, wildlife management areas (WMA), Onsite Sewage Facility (OSSF), and colonias.

**Table 1.** Data sources used for characterization the IBWCNF, HWMD and RVD.


Cultivated crops and urban areas are two types of land cover that can be contributing to NPS pollution. Agricultural and stormwater runoff generated from cultivated crops and urban areas; respectively. Runoff carries various pollutants such as nutrients, sediments, heavy metals, and bacteria which have a negative impact on the receiving waterbodies [41]. In peri-urban areas, agricultural/rural NPS pollution and urban NPS pollution are two types of sources that have gained considerable concern because urban expansion and agriculture intensification may act as a source or sink for contaminants to move toward surface water bodies [42]. Agricultural and urban areas in a watershed have shown in previous studies to be the main contributors to NPS pollution. Another type of NPS pollutants source is the STLR. The main concern with this type of NPS pollutants is the exposure to several hazardous contaminants from the practice of livestock. The improper management of livestock wastes (manure) can cause surface and groundwater pollution [43]. Water pollution from animal production systems can be by direct discharge, runoff, and/or seepage of pollutants to surface or groundwater [44].

OSSFs are designed to treat domestic wastewater using a septic tank for screening and pretreatment and a drain field where pretreated septic effluent is distributed for soil infiltration and final treatment by naturally existing microorganisms [45]. Species with WMA were found close to the coast of each watershed. These NPS pollutants contribute to high bacteria loadings to waterbodies from wildlife in the region. Grazing animals and wildlife can also negatively affect the water quality of runoff and waterbodies with bacterial contamination [46]. In Texas, non-avian wildlife, such as deer or feral hogs, are commonly found to be significant contributors of bacteria to natural streams [43,46]. In addition, colonias are considered the most distressed areas in the United States. They are usually found along the U.S.–Mexico border, which often lacks necessities such as sewer systems, drinkable water, and overall sanitary housing. Many homes within colonias cannot meet county building codes because they lack indoor bathrooms and plumbing, a prerequisite for connection to local water lines and sewage systems [17]. Consequently, colonias can be a potential contributor of NPS pollutants since they lack adequate solid waste disposal and wastewater systems. TCEQ created a classification system to identify the colonias with adequate utilities and the ones that lack basic utilities. The red and yellow classification was the one selected for colonias that potentially carry NPS pollution. Based on the priority classification by the Rural Community Assistance Partnership, OSSFs located in the colonias having a health hazard (red colonias) were assumed to have a greater failure rate of 70%. Conversely, a 30% failure rate (determined based on local expert knowledge) was assigned to areas having the lower priority ratings (yellow colonias) [47]. The term "colonia" refers to a settlement or neighborhood that is an unincorporated rural and peri-urban subdivision along Texas' border with Mexico [48].

STLR and colonias were extracted from TCEQ NPS Pollution database. There are currently limited studies in quantifying NPS pollution in semi-urban areas such as LRGV, where the topography is relatively flat. Furthermore, species and wildlife management areas WMA were considered as well as part of the NPS pollution for the effort in assessing their contaminants to the waterbodies. These were extracted from Texas Parks and Wildlife Department (TPWD). In addition, OSSF locations were mainly extracted from the colonias layer that identified OSSF as their wastewater collection facility. In Jeong's study [47], they utilized a methodology to extract OSSFs from merging address points with colonias. To estimate the number of OSSFs within the watershed, 911 address data for Cameron, Willacy, and Hidalgo counties were obtained. The address points represent the number of homes within a specific area. Combing this layer with the colonias areas, the acquisition of OSSFs was achieved. The colonias layer provided information about this classification and identified the type of colonias with limited wastewater disposal as well as adequate solid waste disposal. OSSFs were extracted from the red and yellow classification from colonias as well as the wastewater community section for onsite systems.

With the collaboration of local stakeholders and state-wide resources, the compilation of PS pollutants was obtained. The PS of pollutants identified in the north and central watersheds include permitted wastewater outfalls (WWO), Texas Land Application Permit (TLAP), Municipal Solid Waste (MSW), Municipal Separate Storm Sewer System (MS4), and desalination plants [48].

There is a substantial contribution of bacteria from wastewater outfalls, which potentially discharges to the waterways. Fecal contamination of water normally results from direct entry of wastewater from a municipal treatment plant into a water body [46,47]. There were two types of WWOs identified in these watersheds: domestic and industrial wastewater discharge. Domestic WWOs discharge less than 1 million gallons per day (MGD) while the ones with a discharge greater than 1 MGD may be either domestic sources or industrial wastewater treatment plant effluent. According to TCEQ, TLAP refers to the spreading of sewage from several applications, such as surface irrigation, evaporation, drain fields, or subsurface land application [49]. MSW facilities not only affect the surface water within the watershed but also groundwater. Closed landfills are commonly unlined and poorly capped and may be sources of a large number of organic compounds to surrounding groundwater and surface water [50]. Polluted stormwater runoff is commonly transported through MS4s and then often discharged, untreated, into local water bodies [51]. MS4s are identified to discharge significant levels of contaminants to waterbodies in the United States and are now one of the major sources of water pollution in the nation [24]. Information about desalination plants was obtained from the Texas Water Development Board (TWDB) to support the PS pollution contribution to the watersheds. Disposing the concentrate from the desalination plant in the surface water is the most common method of concentrate disposal which is considered a point source [52]. These sources can be potential contributors to water quality impairments to the North and Central waterways.

Water quality data were obtained for the three watersheds from the Surface Water Quality Monitoring Information System (SWQMIS) database. The TCEQ maintains SWQMIS database to serve as a repository for surface water data throughout Texas. All the data available in the SWQMIS database have to be collected according to TCEQ surface water quality monitoring standards. Moreover, data must be verified and validated prior to its loading into SWQMIS. HWMD has a TCEQ monitoring station (ID 22003) located at FM 1420 1.65 KM south of the intersection with FM 490 east of Raymondville (Figure 3). In addition, RVD has a TCEQ monitoring station (ID 22004) located at Willacy County Road 445 800 m north of the intersection with FM 3142. Both HWMD and RVD monitoring stations have 8 water quality samples available on the SWQMIS database. Data from both sites were collected by Clean River Programs (CRP) from 2017 to 2019 [53]. For IBWCNF, one TCEQ monitoring station was installed to collect water quality data since 2012. IB-WCNF station ID is 20930 and is located at US 77 2.5 KM south of the intersection of US 77 and FM 2629 in the city of Sebastian. There were 25 water quality samples for the IBWCNF watershed available from SWQMIS from 2012 to 2019 [54,55]. The water quality parameters assessed in this study include the following: bacteria, ammonia, total Kjeldahl nitrogen (TKN), total phosphorus (TP), chlorophyll-a, nitrite, and nitrate. On the other hand, there is currently limited flow data for HWMD and RVD waterways since the monitoring in both stations started in 2017. The data were quantified on a quarterly basis for the period of two years. However, IBWCNF has a flow monitoring station (ID 08470200) installed by USIBWC at the same location of the SWQM near Sebastian that collected data from 2012 to 2020.

posing the concentrate from the desalination plant in the surface water is the most common method of concentrate disposal which is considered a point source [52]. These sources can be potential contributors to water quality impairments to the North and Cen-

Water quality data were obtained for the three watersheds from the Surface Water Quality Monitoring Information System (SWQMIS) database. The TCEQ maintains SWQMIS database to serve as a repository for surface water data throughout Texas. All the data available in the SWQMIS database have to be collected according to TCEQ surface water quality monitoring standards. Moreover, data must be verified and validated prior to its loading into SWQMIS. HWMD has a TCEQ monitoring station (ID 22003) located at FM 1420 1.65 KM south of the intersection with FM 490 east of Raymondville (Figure 3). In addition, RVD has a TCEQ monitoring station (ID 22004) located at Willacy County Road 445 800 m north of the intersection with FM 3142. Both HWMD and RVD monitoring stations have 8 water quality samples available on the SWQMIS database. Data from both sites were collected by Clean River Programs (CRP) from 2017 to 2019 [53]. For IBWCNF, one TCEQ monitoring station was installed to collect water quality data since 2012. IBWCNF station ID is 20930 and is located at US 77 2.5 KM south of the intersection of US 77 and FM 2629 in the city of Sebastian. There were 25 water quality samples for the IBWCNF watershed available from SWQMIS from 2012 to 2019 [54,55]. The water quality parameters assessed in this study include the following: bacteria, ammonia, total Kjeldahl nitrogen (TKN), total phosphorus (TP), chlorophyll-a, nitrite, and nitrate. On the other hand, there is currently limited flow data for HWMD and RVD waterways since the monitoring in both stations started in 2017. The data were quantified on a quarterly basis for the period of two years. However, IBWCNF has a flow monitoring station (ID 08470200) installed by USIBWC at the same location of the SWQM near Sebastian that

**Figure 3.** Location of water quality and flow data monitoring stations. **Figure 3.** Location of water quality and flow data monitoring stations.

### **4. Results 4. Results**

tral waterways.
