Assessment of irrigation and environmental quality
at the hydrological basin level
I. Irrigation quality
J. Causape
´
*
, D. Quı
´
lez, R. Aragu
¨
e
´
s
y Laboratorio de Agronomı
´
a y Medio Ambiente (DGA-CSIC), Centro de Investigacio
´
n y Tecnologı
´
a
Agroalimentaria de Arago
´
n (Diputacio
´
n General de Arago
´
n), Unidad de Suelos y Riegos,
Apdo. 727, 50080-Zaragoza, Spain
Accepted 28 June 2004
Abstract
Irrigated agriculture notably increases crop productivity, but consumes high volumes of water and
may induce off-site pollution of receiving water bodies. The objectives of this paper were to diagnose
the quality of irrigation and to prescribe recommendations aimed at improving irrigation management
and reducing the off-site pollution from a 15,500 ha irrigation district located in the Ebro River Basin
(Spain). Three hydrological basins were selected within the district where the main inputs (irrigation,
precipitation, and groundwater inflows) and outputs (actual crop’s evapotranspiration, surface
drainage outflows, and groundwater outflows) of water were measured or estimated during a
hydrological year. The highest volume of water (I = 1400 mm/year) was applied in the basin with
highly permeable, low water retention, flood irrigated soils where 81% of the total surface was planted
with alfalfa and corn. This basin had the lowest consumptive water use efficiency (CWUE = 45%), the
highest water deficit (WD = 5%) and the highest drainage fraction (DF = 57%). In contrast, the lowest I
(950 mm/year), the highest CWUE (62%), and the lowest WD (2%) and DF (37%) were obtained in
the basin with 60% of the surface covered with deep, high water retention, alluvial valley soils, where
39% of the cultivated surface is sprinkler irrigated and with only 48% of the surface planted with
alfalfa and corn. We concluded that the three most important variables determining the quality of
irrigation and the volume of irrigation return flows in the studied basins were (i) soil characteristics, (ii)
irrigation management and irrigation system, and (iii) crop water requirements. Therefore, the critical
recommendations for improving the quality of irrigation are to (i) increase the efficiency of flood-
irrigation, (ii) change to pressurized systems in the shallow and highly permeable soils, and (iii) reuse
www.elsevier.com/locate/agwat
Agricultural Water Management 70 (2004) 195–209
* Corresponding author. Tel.: +34 976716324; fax: +34 976716335.
E-mail address: jcausape@aragob.es (J. Causape
´
).
0378-3774/$ – see front matter # 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.agwat.2004.06.005