Coping with Rainfall Variability: Dry Spell Mitigation and Implication on Landscape Water Balances in Small-scale Farming Systems in Semi-arid Niger

Abstract

Rainfall variability and inherent dry spells are a reality with severe implications for smallholder agro-ecosystems in semi-arid Sahel. To increase both on- and off-farm biomass production and productivity is challenging with these climate-induced temporal and spatial variations of water. This paper tests the idea that increased vegetation through tree cover may impact water balance in a water-stressed landscape: South-east Niger. Local rainfall data, farming systems data and a landscape water-modelling tool (ArcSWAT) are used. Four production domains (conventional or fertilized combined with millet crop or millet crop plus trees) were assessed for long-term yield and landscape water balance impacts. The dry-spell analysis shows a frequency of dry spells less than 14 days is in the order of one to two dry-spell events per season in 7 years out of 10 years. The occurrence has increased between 1960 and 2004, despite a slight recovery of total annual rainfall amounts since the severe droughts of the 1980s. Results of modelled millet yields and landscape water balances suggest that options exist to enhance landscape productivity. With marginal inputs of fertilizer, millet yields increased fivefold to 2.0–2.4 t ha^− 1, and water productivity improved from 6,000 to 12,000 m³ actual evapotranspiration (ET_a) t^− 1 grain, to an improved 1,700–3,000 m³ ET_a t^− 1 grain. In addition, 10% tree cover in combination with fertilized millet increased yield with marginal or no impact on water partitioning and flows in the landscape. The policy opportunities are complex and urgently needed in view of increased rainfall variability due to expected climate change. To develop sustainable pathways in these landscapes dominated by poor smallholder framers requires water managers to be more innovative and go beyond water resources alone.

Acknowledgements

This research was developed within the research initiative ‘Transformations and Shifts in Production Landscapes for Livelihood Improvements in the Sahel: Building a Partnership in Research’ funded by the NERC-ESPA initiative and ‘Human Dimensions Behind the Greening of the Sahel: Social–Ecological Dynamics in Greened and Non-greened Communities in Niger’ funded by Sida Sarec. Additional support was contributed by FORMAS Formel EXEC for Jennie Barron. The authors thank the students who in various ways contributed in data collection in various MSc and MRes projects at the University of York, the University of Abdou Moumouni, the University of Ouagadougou and the University of Stockholm during 2009/2010.