* Hydropower reserves 12,288 GWh, down 247 GWh
* Agriculture reservoirs at 65 percent capacity
MADRID, Sept 28 (Reuters) - Spain has less water than a week ago to generate hydro power or irrigate crops, the latest official data showed on Tuesday, but water levels are still comfortably above average for the major importer of gas and grain.
Hydroelectric reservoirs held enough to generate 12,288 gigawatt hours, a drop of 247 GWh from last week, the Ministry for the Environment and Rural Affairs said.
With annual demand running at 257,860 GWH, according to national grid operator REE, that hydro capacity alone would be enough to supply Spain's average power needs for 17.4 days.
While reservoir levels have fallen over what Spain's Met Office described as a warmer and drier summer than usual, hydro reserves are 44.4 percent above average due to water left over from an unusually wet winter and spring.
Hydro power generation has dwindled in recent weeks and has pushed up wholesale electricity prices but has still been enough to displace gas-fired plants from the generation mix and halt a weak recovery in gas consumption.
Wholesale power prices affect utilities such as Iberdrola, Endesa, Gas Natural and Hidrocantabrico.
Spain imports more than 99 percent of the 40 billion cubic metres of gas it burns every year, mostly in the form of liquefied natural gas (LNG), of which it is the world's third-biggest importer.
LIGHT RAIN
In line with Met Office forecasts of a warmer and drier autumn than normal, the Ministry recorded rainfall that was 79.2 percent of average for the week to Sept. 26 at 8.5 millimetres .
Reservoirs set aside for consumption including agricultural use were 65.0 percent full, down from 65.7 percent last week but above an average of 41.1 percent.
In Spain's harsh climate, irrigation is vital for growing crops such as maize and for reducing a structural shortfall, which requires imports of at least 10 million tonnes of grain from as far afield as Argentina and Kazakhstan.
Farmers say water reserves are more than adequate for the maize crop, which they have begun harvesting in southern regions, although field work is not due to reach the northern grainbelt until October.
Spanish farmers also irrigate rice, cotton and alfalfa, a key ingredient in animal feed, which is also produced for export.
(Reporting by Martin Roberts, editing by Jane Baird)