The recent modernization of 1.1 Mha of irrigated land in Spain calls for the evaluation of these ... more The recent modernization of 1.1 Mha of irrigated land in Spain calls for the evaluation of these transformations in terms of environmental impact and resource use efficiency. The available data for this evaluation has increased with the transformation (better, digital and spatially distributed data) allowing for the use of distributed soil water and solute movement models. But most hydrological models require soil hydrologic properties that are costly and time-consuming to gather and soil information in Spain is generally scarce. This paper focuses in analyzing the soil hydrologic features in La Violada Irrigation District (VID; a 5234 ha semi-arid irrigated area recently modernized in northeast Spain) usable in soil water models for the evaluation of the new irrigation system. The recent soil map of the VID (presented in a companion paper) gathered the hydrologic and salinity properties of the horizons in the described soil units. The hydraulic conductivity (K s) of the horizons was also assessed by the inverse auger-hole method. From these data, the VID was disaggregated in three homogeneous units according to their hydrologic features and Pedotransfer Functions (PTFs) were built for the whole VID (General Model) and separately for the homogeneous soil units (Distributed Model). These PTFs allowed for obtaining field capacity (FC) and wilting point (WP) from texture and organic matter, while K s depended upon texture and gypsum content. Apparently, there were no salinity issues in VID soils due to irrigation. The high Ca 2 + and Mg 2 + levels in the saturation extract resulted in generally low SAR, what along with the high gypsum and carbonate contents may help to prevent soil degradation by sodicity. As a result, the homogeneous hydrologic zones defined in VID may be used to recommend specific irrigation practices and as the basis for the application of distributed soil water movement models. These hydrologic properties may be applied directly as inputs to the models while the PTFs may allow for setting adequate parameters in nearby areas with similar soils from more readily available soil information (texture, organic matter and gypsum).
Gauging drainage output Estimation of irrigation quality indices Estimation of exported masses Ex... more Gauging drainage output Estimation of irrigation quality indices Estimation of exported masses Exported salts indices Presentation Outline
Results of the irrigation evaluations performed in the second phase of the project “Improvement o... more Results of the irrigation evaluations performed in the second phase of the project “Improvement of the Water Irrigation Integral Management in the Comunidad de Regantes V del Canal de Bardenas” are presented in this paper. An 80 % of the area of the Irrigation District is occupied by soils of residual platforms, and the rest of the soils are alluvial. A soil 1 Estacion Experimental de Aula Dei, CSIC. Apdo. 202. 50080 Zaragoza (Espana). [email protected] 2 Servicio de Investigacion Agraria, DGA. Apdo. 727. 50080 Zaragoza (Espana). 3 L 2 y asociados ingenieria. C/ Aragon 7. Ejea de los Caballeros, Zaragoza (Espana).
Nitrogen (N) pollution induced by irrigated agriculture is a significant environmental problem. T... more Nitrogen (N) pollution induced by irrigated agriculture is a significant environmental problem. The main N inputs and outputs were measured or estimated in the semi-arid La Violada irrigation district (Spain). Data on two periods (1995-98 and 2006-08) were compared and related to observed changes during the decade in cropping patterns and N fertilization and irrigation management. N fertilization exceeded crop N uptake due to over-fertilization of corn (426 kg N/ha in 1995-98 and 332 kg N/ha in 2006-08) and alfalfa (62 kg N/ha). Between the two periods, N fertilization decreased by 56%, primarily due to a change from corn to alfalfa and barley. Accordingly, N losses in the irrigation return flows (IRF) diminished from 31% of the applied fertilizer in 1995-98 to 20% in 2006-08. NO 3 concentrations and NO 3-N loads in the IRF decreased from 40 mg/L and 106 kg N/ha in 1995-98 to 21 mg/L and 22 kg N/ha in 2006-08, due to lower N fertilization, lower corn area and improved irrigation efficiency. N contamination in the IRF will be minimized by increasing the irrigation efficiency and decreasing the corn area and its N fertilization rates, particularly when supplemental organic N is applied at pre-sowing.
One of the main constraints of irrigated agriculture is off-site N pollution due to export of nit... more One of the main constraints of irrigated agriculture is off-site N pollution due to export of nitrate in irrigation return flows (IRF). Models capable of simulating the growth of crops and the N loads in IRF as affected by irrigation and N fertilization may be valuable tools in watershed studies. The Agricultural Policy Environmental eXtender (APEX) model was used to assess best management practices for reducing off-site N loads in the IRF of three Mediterranean irrigated watersheds (Akarsu in Turkey, La Violada in Spain and Sidi Rached in Algeria). The watersheds (ranging from 4013 to 10971 ha) were monitored along three hydrological years to determine the volume of IRF and the NO 3-N concentrations and loads in IRF. APEX was calibrated with the data of the first two years and validated with the last year´s data. APEX adequately simulated crop evapotranspiration and the volume of IRF and N loads in the IRF (errors < 20%). Simulated annual values were in general more accurate than simulated monthly values. APEX predicted that improving irrigation management (change of irrigation system and/or scheduling) will decrease N loads in IRF over current values by 45% (Akarsu), 40% (La Violada), and 8% (Sidi Rached). However, improved N fertilization only will reduce N loads in IRF by 17% (Akarsu) or below 5% (La Violada and Sidi Rached). Improving irrigation management will increase IRF NO 3-N concentrations by 19% in La Violada and will decrease or will remain the same in the other two watersheds. APEX simulations identified the main soils (shallow and low water holding capacity soils) and crops (heavily fertilized or shallow-root crops) N polluters within the studied watersheds. Overall, APEX simulated that the improvement of irrigation performance was the best management strategy to decrease off-site N pollution while maintaining or increasing crop yields in the three studied Mediterranean watersheds.
Diagnosis of water management at the irrigation district level is required for the rational moder... more Diagnosis of water management at the irrigation district level is required for the rational modernisation of the irrigation schemes and the subsequent increase in the efficiency of water allocation and application. Our objectives were to: (i) evaluate the global irrigation performance in the 5282 ha La Violada surface-irrigated district (Ebro River Basin, northeast Spain), and (ii) estimate the water that could potentially be conserved under two scenarios of modernisation and three increased irrigation efficiencies. The main district's water inputs and outputs were measured (irrigation, precipitation, and outflow surface drainage) or estimated (canal releases, lateral surface runoff, municipal wastewaters, and actual evapotranspiration of crops) during the 1995-1998 hydrological years. The annual average water outputs were 23% higher than the corresponding water inputs, presumably due to canal seepage and lateral groundwater inflows from the 14 355 ha dry-land watershed. The district-level irrigation performance was poor (mean 1995-1998 seasonal irrigation consumptive use coefficient (ICUC) = 48%), due to the low distribution (DE) and on-farm (ICUCf) efficiencies (i.e., mean estimates of 83% (DE) and 61% (ICUCf) for the 1995-1996 irrigation seasons). Thus, despite the high volume of applied irrigation water, the actual district ET was 16% lower than the maximum achievable ET, indicating that the water-stressed crops yielded below their maximums. Potential reductions in water allocation were estimated for three ICUC values (65, 75 and 85%) and two scenarios of modernisation (I and II). In scenario I, where the aim was to achieve maximum ET and crop yields, water allocation could be reduced from 8 to 30% of the current allocation. In scenario II, where the aim was to achieve the maximum conservation of water under the actual ET and crop yields, reductions in water allocation would be much higher (from 26 to 43% of current allocation). Thus, significant volumes of water could be conserved in the rehabilitation of this 50-year-old district by increasing the distribution efficiency and, in particular, the on-farm irrigation efficiency.
EGU General Assembly Conference Abstracts, Apr 1, 2013
The conservation of the quality of surface waters demanded by the European Water Framework Direct... more The conservation of the quality of surface waters demanded by the European Water Framework Directive requires, among others, an assessment of the irrigation-induced pollution. The contribution of the irrigation return flows (IRF) to the pollution of the receiving water bodies is given by its pollutant load, since this load determines the quality status or pollutant concentration in these water bodies. The aim of this work was to quantify the annual nitrogen and salt loads in the IRF of four irrigated catchments within the Ebro River Basin: Violada (2006-10), Alcanadre (2008-10), Valcuerna (2010), and Clamor Amarga (2010). The daily flow (Q), salt (EC) and nitrate concentration (NO 3) were measured in the drainage outlets of each basin. The net irrigation-induced salt and nitrogen loads were obtained from these measurements after discounting the salt and nitrogen inputs from outside the catchments and the non-irrigated areas. The N-fertilizer applications were obtained from farmer surveys and animal farming statistical sources. Irrigation water salinity was very low in all catchments (EC < 0.4 dS/m), but IRF salinity was very high in Valcuerna (7.9 dS/m) with underlain saline lutites, high to moderate in Clamor (2.6 dS/m) and Violada (2.1 dS/m) with gypsum-rich soils, and low in Alcanadre (1.0 dS/m) due to dilution in the inefficient traditional flood-irrigation system. Annual salt loads were highest in Valcuerna (11.9 Mg/ha) and lowest in Alcanadre (3.6 Mg/ha) and Clamor (3.3 Mg/ha). Salt load was also high in flood-irrigated Violada (10.3 Mg/ha), but dropped to 2.6 Mg/ha after its modernization to sprinkler irrigation (in 2008-09). N-fertilizer applications ranged from 221 kg/ha in the corn-dominated Valcuerna in 2010 to 63 kg/ha in 2008 in Violada, when farmers barely applied fertilizers due to the irrigation modernization works in progress that year. The highest N applications derived from pig slurry applications by farmers that used their lands as disposal sites for their farm residues. The highest NO 3 concentrations (mean of 113 mg/L) and annual N loads (mean of 38 kg/ha) were found in Valcuerna, the most intense corn sprinkler-irrigated catchment. The lowest NO 3 concentrations (21 mg/L; 5 times lower than Valcuerna) were measured in the Alcanadre flood-irrigated catchment. In contrast, Alcanadre N loads (21 kg/ha) were only about two times lower than in Valcuerna, due to the higher IRF volumes in Alcanadre (353 mm versus 132 mm in Valcuerna). Irrigation modernization in Violada decreased N loads from 20 to 5 kg N/ha (four times lower) due to the sharp reduction of IRF while maintaining NO 3 concentration around 20 mg/L. The only significant contribution of ammonium (17% to the total N load of 13 hg/ha) was found in Clamor, the catchment with highest agro-industrial development. Overall, IRF salt and nitrate concentrations tended to increase and salt and nitrate loads tended to decrease in modernized sprinkler irrigation catchments, but the presence of soluble minerals, the applied inorganic and especially organic N, and the cropping patterns also played a significant role in this behaviour.
The recent modernization of 1.1 Mha of irrigated land in Spain calls for the evaluation of these ... more The recent modernization of 1.1 Mha of irrigated land in Spain calls for the evaluation of these transformations in terms of environmental impact and resource use efficiency. The available data for this evaluation has increased with the transformation (better, digital and spatially distributed data) allowing for the use of distributed soil water and solute movement models. But most hydrological models require soil hydrologic properties that are costly and time-consuming to gather and soil information in Spain is generally scarce. This paper focuses in analyzing the soil hydrologic features in La Violada Irrigation District (VID; a 5234 ha semi-arid irrigated area recently modernized in northeast Spain) usable in soil water models for the evaluation of the new irrigation system. The recent soil map of the VID (presented in a companion paper) gathered the hydrologic and salinity properties of the horizons in the described soil units. The hydraulic conductivity (K s) of the horizons was also assessed by the inverse auger-hole method. From these data, the VID was disaggregated in three homogeneous units according to their hydrologic features and Pedotransfer Functions (PTFs) were built for the whole VID (General Model) and separately for the homogeneous soil units (Distributed Model). These PTFs allowed for obtaining field capacity (FC) and wilting point (WP) from texture and organic matter, while K s depended upon texture and gypsum content. Apparently, there were no salinity issues in VID soils due to irrigation. The high Ca 2 + and Mg 2 + levels in the saturation extract resulted in generally low SAR, what along with the high gypsum and carbonate contents may help to prevent soil degradation by sodicity. As a result, the homogeneous hydrologic zones defined in VID may be used to recommend specific irrigation practices and as the basis for the application of distributed soil water movement models. These hydrologic properties may be applied directly as inputs to the models while the PTFs may allow for setting adequate parameters in nearby areas with similar soils from more readily available soil information (texture, organic matter and gypsum).
Gauging drainage output Estimation of irrigation quality indices Estimation of exported masses Ex... more Gauging drainage output Estimation of irrigation quality indices Estimation of exported masses Exported salts indices Presentation Outline
Results of the irrigation evaluations performed in the second phase of the project “Improvement o... more Results of the irrigation evaluations performed in the second phase of the project “Improvement of the Water Irrigation Integral Management in the Comunidad de Regantes V del Canal de Bardenas” are presented in this paper. An 80 % of the area of the Irrigation District is occupied by soils of residual platforms, and the rest of the soils are alluvial. A soil 1 Estacion Experimental de Aula Dei, CSIC. Apdo. 202. 50080 Zaragoza (Espana). [email protected] 2 Servicio de Investigacion Agraria, DGA. Apdo. 727. 50080 Zaragoza (Espana). 3 L 2 y asociados ingenieria. C/ Aragon 7. Ejea de los Caballeros, Zaragoza (Espana).
Nitrogen (N) pollution induced by irrigated agriculture is a significant environmental problem. T... more Nitrogen (N) pollution induced by irrigated agriculture is a significant environmental problem. The main N inputs and outputs were measured or estimated in the semi-arid La Violada irrigation district (Spain). Data on two periods (1995-98 and 2006-08) were compared and related to observed changes during the decade in cropping patterns and N fertilization and irrigation management. N fertilization exceeded crop N uptake due to over-fertilization of corn (426 kg N/ha in 1995-98 and 332 kg N/ha in 2006-08) and alfalfa (62 kg N/ha). Between the two periods, N fertilization decreased by 56%, primarily due to a change from corn to alfalfa and barley. Accordingly, N losses in the irrigation return flows (IRF) diminished from 31% of the applied fertilizer in 1995-98 to 20% in 2006-08. NO 3 concentrations and NO 3-N loads in the IRF decreased from 40 mg/L and 106 kg N/ha in 1995-98 to 21 mg/L and 22 kg N/ha in 2006-08, due to lower N fertilization, lower corn area and improved irrigation efficiency. N contamination in the IRF will be minimized by increasing the irrigation efficiency and decreasing the corn area and its N fertilization rates, particularly when supplemental organic N is applied at pre-sowing.
One of the main constraints of irrigated agriculture is off-site N pollution due to export of nit... more One of the main constraints of irrigated agriculture is off-site N pollution due to export of nitrate in irrigation return flows (IRF). Models capable of simulating the growth of crops and the N loads in IRF as affected by irrigation and N fertilization may be valuable tools in watershed studies. The Agricultural Policy Environmental eXtender (APEX) model was used to assess best management practices for reducing off-site N loads in the IRF of three Mediterranean irrigated watersheds (Akarsu in Turkey, La Violada in Spain and Sidi Rached in Algeria). The watersheds (ranging from 4013 to 10971 ha) were monitored along three hydrological years to determine the volume of IRF and the NO 3-N concentrations and loads in IRF. APEX was calibrated with the data of the first two years and validated with the last year´s data. APEX adequately simulated crop evapotranspiration and the volume of IRF and N loads in the IRF (errors < 20%). Simulated annual values were in general more accurate than simulated monthly values. APEX predicted that improving irrigation management (change of irrigation system and/or scheduling) will decrease N loads in IRF over current values by 45% (Akarsu), 40% (La Violada), and 8% (Sidi Rached). However, improved N fertilization only will reduce N loads in IRF by 17% (Akarsu) or below 5% (La Violada and Sidi Rached). Improving irrigation management will increase IRF NO 3-N concentrations by 19% in La Violada and will decrease or will remain the same in the other two watersheds. APEX simulations identified the main soils (shallow and low water holding capacity soils) and crops (heavily fertilized or shallow-root crops) N polluters within the studied watersheds. Overall, APEX simulated that the improvement of irrigation performance was the best management strategy to decrease off-site N pollution while maintaining or increasing crop yields in the three studied Mediterranean watersheds.
Diagnosis of water management at the irrigation district level is required for the rational moder... more Diagnosis of water management at the irrigation district level is required for the rational modernisation of the irrigation schemes and the subsequent increase in the efficiency of water allocation and application. Our objectives were to: (i) evaluate the global irrigation performance in the 5282 ha La Violada surface-irrigated district (Ebro River Basin, northeast Spain), and (ii) estimate the water that could potentially be conserved under two scenarios of modernisation and three increased irrigation efficiencies. The main district's water inputs and outputs were measured (irrigation, precipitation, and outflow surface drainage) or estimated (canal releases, lateral surface runoff, municipal wastewaters, and actual evapotranspiration of crops) during the 1995-1998 hydrological years. The annual average water outputs were 23% higher than the corresponding water inputs, presumably due to canal seepage and lateral groundwater inflows from the 14 355 ha dry-land watershed. The district-level irrigation performance was poor (mean 1995-1998 seasonal irrigation consumptive use coefficient (ICUC) = 48%), due to the low distribution (DE) and on-farm (ICUCf) efficiencies (i.e., mean estimates of 83% (DE) and 61% (ICUCf) for the 1995-1996 irrigation seasons). Thus, despite the high volume of applied irrigation water, the actual district ET was 16% lower than the maximum achievable ET, indicating that the water-stressed crops yielded below their maximums. Potential reductions in water allocation were estimated for three ICUC values (65, 75 and 85%) and two scenarios of modernisation (I and II). In scenario I, where the aim was to achieve maximum ET and crop yields, water allocation could be reduced from 8 to 30% of the current allocation. In scenario II, where the aim was to achieve the maximum conservation of water under the actual ET and crop yields, reductions in water allocation would be much higher (from 26 to 43% of current allocation). Thus, significant volumes of water could be conserved in the rehabilitation of this 50-year-old district by increasing the distribution efficiency and, in particular, the on-farm irrigation efficiency.
EGU General Assembly Conference Abstracts, Apr 1, 2013
The conservation of the quality of surface waters demanded by the European Water Framework Direct... more The conservation of the quality of surface waters demanded by the European Water Framework Directive requires, among others, an assessment of the irrigation-induced pollution. The contribution of the irrigation return flows (IRF) to the pollution of the receiving water bodies is given by its pollutant load, since this load determines the quality status or pollutant concentration in these water bodies. The aim of this work was to quantify the annual nitrogen and salt loads in the IRF of four irrigated catchments within the Ebro River Basin: Violada (2006-10), Alcanadre (2008-10), Valcuerna (2010), and Clamor Amarga (2010). The daily flow (Q), salt (EC) and nitrate concentration (NO 3) were measured in the drainage outlets of each basin. The net irrigation-induced salt and nitrogen loads were obtained from these measurements after discounting the salt and nitrogen inputs from outside the catchments and the non-irrigated areas. The N-fertilizer applications were obtained from farmer surveys and animal farming statistical sources. Irrigation water salinity was very low in all catchments (EC < 0.4 dS/m), but IRF salinity was very high in Valcuerna (7.9 dS/m) with underlain saline lutites, high to moderate in Clamor (2.6 dS/m) and Violada (2.1 dS/m) with gypsum-rich soils, and low in Alcanadre (1.0 dS/m) due to dilution in the inefficient traditional flood-irrigation system. Annual salt loads were highest in Valcuerna (11.9 Mg/ha) and lowest in Alcanadre (3.6 Mg/ha) and Clamor (3.3 Mg/ha). Salt load was also high in flood-irrigated Violada (10.3 Mg/ha), but dropped to 2.6 Mg/ha after its modernization to sprinkler irrigation (in 2008-09). N-fertilizer applications ranged from 221 kg/ha in the corn-dominated Valcuerna in 2010 to 63 kg/ha in 2008 in Violada, when farmers barely applied fertilizers due to the irrigation modernization works in progress that year. The highest N applications derived from pig slurry applications by farmers that used their lands as disposal sites for their farm residues. The highest NO 3 concentrations (mean of 113 mg/L) and annual N loads (mean of 38 kg/ha) were found in Valcuerna, the most intense corn sprinkler-irrigated catchment. The lowest NO 3 concentrations (21 mg/L; 5 times lower than Valcuerna) were measured in the Alcanadre flood-irrigated catchment. In contrast, Alcanadre N loads (21 kg/ha) were only about two times lower than in Valcuerna, due to the higher IRF volumes in Alcanadre (353 mm versus 132 mm in Valcuerna). Irrigation modernization in Violada decreased N loads from 20 to 5 kg N/ha (four times lower) due to the sharp reduction of IRF while maintaining NO 3 concentration around 20 mg/L. The only significant contribution of ammonium (17% to the total N load of 13 hg/ha) was found in Clamor, the catchment with highest agro-industrial development. Overall, IRF salt and nitrate concentrations tended to increase and salt and nitrate loads tended to decrease in modernized sprinkler irrigation catchments, but the presence of soluble minerals, the applied inorganic and especially organic N, and the cropping patterns also played a significant role in this behaviour.
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