Integrated Surface-Groundwater Modelling of Nitrate Concentration in Mediterranean Rivers, the Júcar River Basin District, Spain

[EN] High nutrient discharge from groundwater (GW) into surface water (SW) have multiple undesirable effects on river water quality. With the aim to estimate the impact of anthropic pressures and river-aquifer interactions on nitrate status in SW, this study integrates two hydrological simulation and water quality models. PATRICAL models SW-GW interactions and RREA models streamflow changes due to human activity. The models were applied to the Jucar River Basin District (RBD), where 33% of the aquifers have a concentration above 50 mg NO3-/L. As a result, there is a direct linear correlation between the nitrate concentration in rivers and aquifers (Jucar r(2) = 0.9, and Turia r(2) = 0.8), since in these Mediterranean basins, the main amount of river flows comes from groundwater discharge. The concentration of nitrates in rivers and GW tends to increase downstream of the district, where artificial surfaces and agriculture are concentrated. The total NO3- load to Jucar RBD rivers was estimated at 10,202 tN/year (239 kg/km(2)/year), from which 99% is generated by diffuse pollution, and 3378 tN/year (79 kg/km(2)/year) is discharged into the Mediterranean Sea. Changes in nitrate concentration in the RBD rivers are strongly related to the source of irrigation water, river-aquifer interactions, and flow regulation. The models used in this paper allow the identification of pollution sources, the forecasting of nitrate concentration in surface and groundwater, and the evaluation of the efficiency of measures to prevent water degradation, among other applications.The first author's research is partially funded by a PhD scholarship from the food research stream of the program "Colombia Cientifica-Pasaporte a la Ciencia", granted by the Colombian Institute for Educational Technical Studies Abroad (Instituto Colombiano de Credito Educativo y Estudios Tecnicos en el Exterior, ICETEX). The authors thank the Spanish Research Agency (AEI) for the financial support to RESPHIRA project (PID2019-106322RB-100)/AEI/10.13039/501100011033.Dorado-Guerra, DY.; Paredes Arquiola, J.; Pérez-Martín, MÁ.; Tafur Hermann, H. (2021). Integrated Surface-Groundwater Modelling of Nitrate Concentration in Mediterranean Rivers, the Júcar River Basin District, Spain. Sustainability. 13(22):1-21. https://doi.org/10.3390/su132212835S121132

Caracterización edafoclimática de la zona productora de lima ácida Tahití (Citrus latifolia Tanaka) en el Tolima (Colombia), afectada por una fisiopatía

In the Department of Tolima, Colombia, a disorder associated with the death of plant structures and dieback was observed in four-year old trees. A similar disorder known as Wood Pocket has been reported in the United States and Mexico. In California (USA) the main cause of the disorder was attributed to the planted genetic material and the problem was solved using resistant rootstock. In the study area the rootstock influence has not been analyzed yet. According to the scarce literature, this disorder is closely associated with warm dry weather. The study area has predominant high temperature conditions, water imbalance, and well drained soils. The above factors lead to plants having low water availability to supply the high atmospheric demand, typically being in deficit throughout the plant´s productive period. Poor agricultural practices in orchards, such as water management, i.e., water shortage or inadequate irrigation intensifies the problem. This plant disorder is a generalized condition of orchards in the warmest area of Tolima. The soil and climatic characteristics of the production area, which benefit or enhance the development of the disorder were identified. The results of this study should help generate management recommendations in the affected areas as well as preventing future cases of this disorder.En el departamento del Tolima se observan árboles afectados por una fisiopatía que induce muerte de estructuras en individuos de aproximadamente 4 años de edad. Una situación similar fue reportada para Estados Unidos y México, asociado a una fisiopatía, denominada Wood Pocket. Se asumió como causa principal la susceptibilidad del material, dado que en California (EE.UU.) el problema se solucionó con el uso de patrones resistentes. En la zona de estudio aún no se analiza la influencia de los porta-injertos. La literatura reporta que esta fisiopatía, o desorden fisiológico, se potencia en clima cálido seco. La zona de estudio no sólo presenta condiciones de altas temperaturas y de desbalance hídrico, sino además de altas velocidades de infiltración en el suelo. Los factores anteriores conllevan a que las plantas tengan baja disponibilidad de agua para suplir la alta demanda atmosférica, encontrándose típicamente en déficit durante toda la época productiva. Las malas prácticas agrícolas en el manejo hídrico de los huertos, inadecuada aplicación del riego hace que el problema se intensifique. La fisiopatía es una condición generalizada de los huertos de la zona más cálida del Tolima, por lo cual fue necesario identificar las características edafo-climáticas, que benefician o potencian el desarrollo del problema. Los resultados y las recomendaciones de manejo permitirán a los productores generar programas de manejo en zonas afectadas y llegar a prevenir el desorden, donde aún no se presenta

Integrated Surface-Groundwater Modelling of Nitrate Concentration in Mediterranean Rivers, the Júcar River Basin District, Spain

High nutrient discharge from groundwater (GW) into surface water (SW) have multiple undesirable effects on river water quality. With the aim to estimate the impact of anthropic pressures and river–aquifer interactions on nitrate status in SW, this study integrates two hydrological simulation and water quality models. PATRICAL models SW–GW interactions and RREA models streamflow changes due to human activity. The models were applied to the Júcar River Basin District (RBD), where 33% of the aquifers have a concentration above 50 mg NO3−/L. As a result, there is a direct linear correlation between the nitrate concentration in rivers and aquifers (Júcar r2 = 0.9, and Turia r2 = 0.8), since in these Mediterranean basins, the main amount of river flows comes from groundwater discharge. The concentration of nitrates in rivers and GW tends to increase downstream of the district, where artificial surfaces and agriculture are concentrated. The total NO3− load to Júcar RBD rivers was estimated at 10,202 tN/year (239 kg/km2/year), from which 99% is generated by diffuse pollution, and 3378 tN/year (79 kg/km2/year) is discharged into the Mediterranean Sea. Changes in nitrate concentration in the RBD rivers are strongly related to the source of irrigation water, river–aquifer interactions, and flow regulation. The models used in this paper allow the identification of pollution sources, the forecasting of nitrate concentration in surface and groundwater, and the evaluation of the efficiency of measures to prevent water degradation, among other applications

Influencia del riego y la fertilización en el rendimiento y calidad de lima ácida tahití (Citrus latifoliaTanaka)

Los cítricos son capaces de crecer y fructificar en condiciones ambientales muy diversas, desde climas subtropicales relativamente fríos hasta zonas tropicales cálidas. Se han encontrado relaciones estrechas con factores ambientales, entre los que se encuentran un régimen de temperaturas moderadamente bajas, en condiciones subtropicales, y el estrés hídrico en el trópico para activar la floración, lo cual hace que el suministro de agua sea muy importante en la producción. Se evaluó el efecto del sistema de riego localizado de alta frecuencia y la fertilización sobre el rendimiento y calidad del cultivo de lima acida Tahití, en tres localidades de Colombia; Espinal (Tolima) a 335 msnm, Lebrija (Santander) a 1033 msnm y Santo Tomas (Atlántico) a 19 msnm. Las láminas de riego evaluadas se basaron en porcentajes de la evapotranspiración de referencia (ETo) así: L1= 50%ETo, L2= 70%ETo y L3= 100%ETo. Los tres niveles de fertilización fueron: N1= según el análisis químico del suelo/requerimientos de la planta, N2= doble de la fertilización recomendada en N1 y N3 = fertilización utilizada por el productor. La frecuencia de fertilización fue quincenal. Las variables de respuesta fueron: rendimiento, peso del fruto, diámetro ecuatorial y polar del fruto, grosor de la cáscara, peso y porcentaje de jugo, acidez, sólidos solubles y contenido de vitamina C.//Abstract: Citrus is able to grow and flourish in a variety of environmental conditions from relatively cold climates to subtropical warm tropical areas. It has been found a close relationship between environmental factors, such as moderately low temperatures in subtropical conditions, and water stress in the tropics that trigger flowering, which makes water supply a very important factor associated with yield. The effect of drip irrigation system and high frequency fertilization on crop yield and quality of Tahiti lime was evaluated at three locations in Colombia, i.e., Espinal (Tolima) at 335 a.m.s.l., Lebrija (Santander) at 1033 a.m.s.l., and Santo Tomas (Atlántico) at 19 a.m.s.l. Slidesevaluatedirrigationrateswere based onreference evapotranspiration(ETo) as follows: L1= 50% ETo, L2= 70% ETo y L3= 100% ETo.The three levels of fertilization were: N1 = according to the chemical analysis soil / plant requirements, N2 = twice the recommended N1 and N3 fertilization = fertilizer used by the grower. The frequency of fertilization was fortnightly. The response variables were: yield, fruit weight, equatorial and polar diameter fruit, shell thickness, weight and juice percentage, acidity, soluble solids and vitamin C content. In Espinal, where there were sandy loams with a very low nutrition state and a negative water balance throughout the year, an optimal response was observed in the irrigation sheet with the greatest water applied (L3), represented mainly in the yield (number and weight of fruits (average 80 g)) and quality production that place it in category C (technical standard Colombian acidfor Tahiti lime under NTC 4087), which is acceptable for export. In Lebrija, the optimal water availability of 10 months per year, makes the production of Tahiti lime an energetically economic activity, even in soils with characteristics suitable for cultivation, such as sandy soils with high chemical weathering, where the presence of acid pH is not a limiting factor for cultivation. The highest values for size and fruit weight (average 109 g) were achieved with the interaction of treatments L3 x N1, placing this production in category B (according to NTC 4087). In Santo Tomás, the production was limited and a productive state was not observed before the fourth year, an age at which the yield had stabilized for other localities, starting on the second year. The low production resulting by the soil conditions (poor soils) and a water deficit during most of the year makes the productive activity of Tahiti lime unprofitable for the region, given the need for high technology investment in irrigation and nutrition.Maestrí

Machine learning models to predict nitrate concentration in a river basin

[EN] Aquifer-stream interactions affect the water quality in Mediterranean areas; therefore, the coupling of surface water and groundwater models is generally used to solve water-planning and pollution problems in river basins. However, their use is limited because model inputs and outputs are not spatially and temporally linked, and the data update and fitting are laborious tasks. Machine learning models have shown great potential in water quality simulation, as they can identify the statistical relationship between input and output data without the explicit requirement of knowing the physical processes. This allows the ecological, hydrological, and environmental variables that influence water quality to be analysed with a holistic approach. In this research, feature selection (FS) methods and algorithms of artificial intelligence¿random forest (RF) and eXtreme Gradient Boosting (XGBoost) trees¿are used to simulate nitrate concentration and determine the main drivers related to nitrate pollution in Mediterranean streams. The developed models included 19 inputs and sampling of nitrate concentration in 159 surface water quality-gauging stations as explanatory variables. The models were trained on 70 percent data, with 30 percent used to validate the predictions. Results showed that the combination of FS method with local knowledge about the dataset is the best option to improve the model¿s performance, while RF and XGBoost simulate the nitrate concentration with high performance (r=0.93 and r=0.92, respectively). The final ranking, based on the relative importance of the variables in the RF and XGBoost models, showed that, regarding nitrogen and phosphorus concentration, the location explained 87 percent of the nitrate variability. RF and XGBoost predicted nitrate concentration in surface water with high accuracy without using conditions or parameters of entry and enabled the observation of different relationships between drivers. Thus, it is possible to identify and delimit zones with a spatial risk of pollution and approaches to implementing solutionsWe appreciate the help provided by the Júcar River Basin District Authority (CHJ), who gathered field data. The first author's research is partially funded by a PhD scholarship from the food research stream of the program `Colombia Científica Pasaporte a la Ciencia, granted by the Colombian Institute for Educational Technical Studies Abroad (Instituto Colombiano de Crédito Educativo y Estudios Técnicos en el Exterior, ICETEX). The authors thank the Spanish Research Agency (AEI) for the financial support to RESPHIRA project (PID2019- 106322RB-100)/AEI/10.13039/501100011033.Dorado-Guerra, DY.; Corzo-Pérez, G.; Paredes Arquiola, J.; Pérez-Martín, MÁ. (2022). Machine learning models to predict nitrate concentration in a river basin. Environmental Research Communications. 4(12):1-18. https://doi.org/10.1088/2515-7620/acabb711841