Modeling Irrigation Water Consumption at Microdata Level in the Census of Agriculture 2009 (Spain)
Jorge Saralegui, Fernando Celestino-Rey
Environmental and Business Statistics, INE (Spain), Madrid, Spain

During the first half of 2010, INE (Spain) carried out the second phase of the Agricultural Census 2009 by collecting additional data through the Survey of Production Methods (EMP2009). It was addressed to a sample of 60,000 holdings drawn from the census frame (1,400,00 holdings approximately). One of the goals of the survey (also required by EU regulation) was to estimate at the microdata level (holding) the volume of irrigation water used during the agricultural year 2009.

Preliminary studies recommended not to include in the survey forms the quantity of water consumed as an specific question, mainly due to the risk of high measurement errors. Therefore it was decided to launch a project of model assisted estimation in several stages, combining direct observations with exogenous data from diverse administrative and statistical sources.

I) Model of water requirements. Administrative sources provide agro-meteorological data on actual and net rainfall and transpiration adjusted to each particular crop within a particular area belonging to a national network of 800 irrigation areas. After several complex treatments using available databases, the theoretical water requirements per crop in a given month is estimated.

II) Models of irrigation efficiency. In this stage the actual consumption of irrigation water per crop is imputed and aggregated within each holding. At this end, detailed coefficients have been provided to INE by the Ministry of Environment, Rural and Marine Affaires (MARM) according to the irrigation technique (as collected in the EMP2009) and the conservation status of irrigation equipment within the area.

III) Final estimation and calibration. In this last stage the sampling design weights (corrected for non-response) are calculated. External data from the census (crop irrigated area) and the annual environmental Survey on Water Use (Ine) are used for control and/or calibration of the weights. The paper presents the first results and a brief assessment of the quality of the imputation.

Regulation (EC) No. 1166/2008 of the European Parliament and of the Council of 19 november 2008 on farm structure and the survey on agricultural production methods.

Carcelén, Vicente. (1999) Estimations of the water demand in the irrigation planning. In: XVII National Congress of Irrigation. Murcia (Spain).

Keywords: Water statistics; Irrigation water consumption; Water use + agricultural census; Evapotranspiration models;

Biography: Director, Environment and Structural Business Statistics (INE, Spain)

Mathematics statistician, during his first years in Ine he acted as survey statistician in a variety of census and survey projects, as well as a methodologist in the social surveys sampling design department.

Subsequently Director, Social Statistics 1991-2000; Director, Methods and Statistical Techniques 2000-2005. During that period he acted as national principal researcher in the Eurarea R&D project on small areas estimation.

At present, Director of Structural Business and Environmental Statistics. This unit covers, in addition to environmental statistics, the annual structural surveys in the manufacturing and services sectors.