Loading...
Publication
Necessidades hídricas do olival no Alentejo e projecções para o período 2071-2100
| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 613.92 KB | Adobe PDF |
Authors
Advisor(s)
Abstract(s)
O olival é uma cultura típica mediterrânica, adaptada a situações de escassez de água.
Sendo tradicionalmente uma cultura de sequeiro, poderá no futuro só ser viável em
regadio. As necessidades hídricas da cultura são estimadas recorrendo a um modelo
empírico de balanço hídrico do solo, para um período de tempo longo, que permitirá
captar a sua variabilidade e detectar eventuais tendências.
Usando séries diárias de temperatura máxima e mínima, humidade relativa, insolação
e velocidade do vento em Beja calcula-se a evapotranspiração de referência ETo pelo
método de Penman-Monteith, no período 1965-2000. Valores diários de precipitação
no mesmo período são utilizados na simulação diária do balanço hídrico, considerando
um solo representativo. A simulação para os cenários futuros foi feita numa base
mensal. Projecções mensais de temperatura máxima e mínima e precipitação geradas
pelo modelo regional de clima PRECIS para os cenários A2 e B2, no período 2071-2100
permitiram estimar ETo seguindo o preconizado pela FAO-56 para dados incompletos,
e efectuar o balanço hídrico num passo de tempo mensal.
A análise de frequências das estimativas mensais e anuais das necessidades hídricas da
cultura permitiu caracterizar os anos mais secos/mais húmidos e detectar eventuais
tendências no período histórico analisado. As necessidades históricas são comparadas
com as resultantes dos cenários climáticos. No olival projecta-se um acréscimo nas necessidades globais de rega superior a 40% que corresponde a acréscimos da ET
máxima de 10 a 15% e a decréscimos da precipitação de 25 a 30% nos cenários A2 e B2
respectivamente. No período de registos históricos analisa-se a evolução temporal da
razão entre ET actual e ET máxima acumuladas durante diferentes intervalos de tempo
e a sua relação com as secas evidenciando uma razão 0.4-0.5 como indicador de
escassez e seca no olival, a 12 meses de acumulação. Pretende-se com este trabalho quantificar alterações das necessidades hídricas de
uma cultura tradicionalmente adaptada à região e identificar futuras situações de
escassez que possam apoiar medidas de adaptação e uma melhor gestão futura dos
recursos solo e água.
The olive tree is a typical mediterranean crop, well adapted to water scarcity. It is a traditional rainfed crop that in the future possibly will need to be irrigated for viability. Olive net irrigation requirements are estimated using an empirical soil water balance over a time period of 36 years thus allowing to characterize variability and to capture tendencies. The reference evapotranspiration in Beja is computed in the period 1965-2000 from daily maximum and minimum temperature, relative humidity, sunshine and wind speed using the Penman-Monteith equation. Daily ETo and precipitation are used in the water balance simulation, considering a representative soil and olive orchard. The water balance simulation under scenarios A2 and B2 was carried on a monthly time scale with ETo, computed with maximum and minimum temperatures, following FAO- 56 procedures and precipitation obtained from the regional climate model PRECIS for the period 2071-2100,. Frequency analysis of net irrigation requirements of olive on a monthly and annual basis allowed to characterize drought/wet years and to scan tendencies over the historical record period. Past water requirements are compared with those derived from climate projections. For the olive crop an increase of more than 40% in net irrigation requirements is projected under A2 and B2 scenarios which correspond to an increase of 10 to 15% in maximum ET and a 25 to 30% decrease in precipitation. Additionally the time evolution of the ratio actual ET / maximum ET cumulated over several months and its relations with droughts is studied suggesting an overall 12- months ratio around 0.4-0.5 as a drought water scarcity threshold. The aim of this paper is to quantify changes in water requirements of traditional olive orchards well adapted to the region and identify future water scarcity situations supporting adaptation measures and a better soil and water management in the near future.
The olive tree is a typical mediterranean crop, well adapted to water scarcity. It is a traditional rainfed crop that in the future possibly will need to be irrigated for viability. Olive net irrigation requirements are estimated using an empirical soil water balance over a time period of 36 years thus allowing to characterize variability and to capture tendencies. The reference evapotranspiration in Beja is computed in the period 1965-2000 from daily maximum and minimum temperature, relative humidity, sunshine and wind speed using the Penman-Monteith equation. Daily ETo and precipitation are used in the water balance simulation, considering a representative soil and olive orchard. The water balance simulation under scenarios A2 and B2 was carried on a monthly time scale with ETo, computed with maximum and minimum temperatures, following FAO- 56 procedures and precipitation obtained from the regional climate model PRECIS for the period 2071-2100,. Frequency analysis of net irrigation requirements of olive on a monthly and annual basis allowed to characterize drought/wet years and to scan tendencies over the historical record period. Past water requirements are compared with those derived from climate projections. For the olive crop an increase of more than 40% in net irrigation requirements is projected under A2 and B2 scenarios which correspond to an increase of 10 to 15% in maximum ET and a 25 to 30% decrease in precipitation. Additionally the time evolution of the ratio actual ET / maximum ET cumulated over several months and its relations with droughts is studied suggesting an overall 12- months ratio around 0.4-0.5 as a drought water scarcity threshold. The aim of this paper is to quantify changes in water requirements of traditional olive orchards well adapted to the region and identify future water scarcity situations supporting adaptation measures and a better soil and water management in the near future.
Description
Keywords
Olea europaea Olival Necessidade de água Alteração climática Seca Escassez de água Olive Water requirements Drought Water avaibility
Citation
Paulo, A. & Pinto, H. R. (2014). Necessidades hídricas do olival no Alentejo e projecções para o período 2071-2100. Revista da Unidade de Investigação do Instituto Politécnico de Santarém, 4 (2): 148-162
Publisher
Unidade de Investigação do Instituto Politécnico de Santarém (UIIPS)