Didier Delmon

Bio: Didier Delmon is an academic researcher. The author has contributed to research in topics: Canopy & Transpiration. The author has an hindex of 1, co-authored 1 publications receiving 80 citations.

Measurement and estimation of plastic greenhouse reference evapotranspiration in a Mediterranean climate

Abstract: The standard FAO methodology for the determination of crop water requirements uses the product of reference evapotranspiration (ETo) and crop coefficient values. This methodology can be also applied to soil-grown plastic greenhouse crops, which occupy extended areas in the Mediterranean basin, but there are few data assessing methodologies for estimating ETo in plastic greenhouses. Free-drainage lysimeters were used between 1993 and 2004 to measure ETo inside a plastic greenhouse with a perennial grass in Almeria, south-eastern Spain. Mean daily measured greenhouse ETo ranged from values slightly less than 1 mm day−1 during winter to values of approximately 4 mm day−1 during summer in July. When the greenhouse surface was whitened from March to September (a common practice to control temperature), measured ETo was reduced by an average of 21.4%. Different methodologies to calculate ETo were checked against the measurements in the greenhouse without and with whitening. The methods that performed best in terms of accuracy and statistics were: FAO56 Penman–Monteith with a fixed aerodynamic resistance of 150 s m−1, FAO24 Pan Evaporation with a constant Kp of 0.79, a locally-calibrated radiation method and Hargreaves. Given the data requirements of the different methods, the Hargreaves and the radiation methods are recommended for the calculation of greenhouse ETo because of their simplicity.

Mitigating the Water Footprint of Export Cut Flowers from the Lake Naivasha Basin, Kenya

Abstract: Kenya’s cut-flower industry has been praised as an economic success as it contributed an annual average of US$ 141 million foreign exchange (7 % of Kenyan export value) over the period 1996–2005 and about US$ 352 million in 2005 alone. The industry also provides employment, income and infrastructure such as schools and hospitals for a large population around Lake Naivasha. On the other hand, the commercial farms have been blamed for causing a drop in the lake level, polluting the lake and for possibly affecting the lake’s biodiversity. The objective of this study is to quantify the water footprint within the Lake Naivasha Basin related to cut flowers and analyse the possibility to mitigate this footprint by involving cut-flower traders, retailers and consumers overseas. The water footprint of one rose flower is estimated to be 7–13 litres. The total virtual water export related to export of cut flowers from the Lake Naivasha Basin was 16 Mm3/yr during the period 1996–2005 (22 % green water; 45 % blue water; 33 % grey water). Our findings show that, although the decline in the lake level can be attributed mainly to the commercial farms around the lake, both the commercial farms and the smallholder farms in the upper catchment are responsible for the lake pollution due to nutrient load. The observed decline in the lake level and deterioration of the lake’s biodiversity calls for sustainable management of the basin through pricing water at its full cost and other regulatory measures. Pricing water at full marginal cost is important, but the conditions in Kenya are unlikely to result in serious steps to full-cost pricing, since many farmers resist even modest water price increases and government is lacking means of enforcement. We propose an alternative in this study that can be implemented with a focus on sustainable water use in flower farming around Lake Naivasha alone. The proposal involves a water-sustainability agreement between major agents along the cut-flower supply chain and includes a premium to the final product at the retailer end of the supply chain. Such a ‘water sustainability premium’ will raise awareness among flower consumers and—when channelled back to the farmers—facilitate the flower farms to install the necessary equipment and implement the right measures to use water in a sustainable manner. The collected premiums will generate a fund that can be used for financing measures to reduce the water footprint and to improve watershed management.