A new 1 km global IIASA-IFPRI cropland percentage map for the baseline year 2005 has been developed which integrates a number of individual cropland maps at global to regional to national scales. The individual map products include existing global land cover maps such as GlobCover 2005 and MODIS v.5, regional maps such as AFRICOVER and national maps from mapping agencies and other organizations. The different products are ranked at the national level using crowdsourced data from Geo-Wiki to create a map that reflects the likelihood of cropland. Calibration with national and subnational crop statistics was then undertaken to distribute the cropland within each country and subnational unit. The new IIASA-IFPRI cropland product has been validated using very high-resolution satellite imagery via Geo-Wiki and has an overall accuracy of 82.4%. It has also been compared with the EarthStat cropland Global Change Biology (2015Biology ( ) 21, 1980Biology ( -1992Biology ( , doi: 10.1111 product and shows a lower root mean square error on an independent data set collected from Geo-Wiki. The first ever global field size map was produced at the same resolution as the IIASA-IFPRI cropland map based on interpolation of field size data collected via a Geo-Wiki crowdsourcing campaign. A validation exercise of the global field size map revealed satisfactory agreement with control data, particularly given the relatively modest size of the field size data set used to create the map. Both are critical inputs to global agricultural monitoring in the frame of GEOGLAM and will serve the global land modelling and integrated assessment community, in particular for improving land use models that require baseline cropland information. These products are freely available for downloading from the http://cropland.geo-wiki.org website.

In this paper, we study the impact of climate change on river regimes in several parts of Africa, and we look at the most probable causes of these changes either climatically or anthropogenically driven. We study time series of updated monthly and annual runoff of rivers of North Africa, West Africa (Sahelian and humid tropical regions) and Central Africa, including the largest river basins: Niger and Volta rivers in West Africa, and Congo and Ogooue rivers in Central Africa. The recent years are studied in the perspective of multi-decadal variability. In West Africa and in a part of Central Africa, the climate has changed since 1970, and rainfall has not returned to previous annual amounts, except in Equatorial Africa. The consequences of the long-lasting drought are, depending on the area concerned, the modification of seasonal regimes (Equatorial area), the groundwater table decrease (Tropical humid area) and the land cover degradation (Sahelian area). The increasing number of dams and of agricultural areas also plays a major role on the modification of river regimes. The population increase will continue to impact on the environment: land cover change, deforestation, agriculture and increasing number of dams will be associated with a reduction of water and sediment discharges to the sea, and major impacts on downstream ecosystems and coastal areas. It seems necessary to share with stakeholders a comprehensive approach of the water cycle from the basin to the sea, to prevent long-lasting damages to ecosystems and infrastructures.

The study relates groundwater quality to land use types in Lagos State. Fourteen samples were collected from hand dug wells and boreholes, seven each from rural and urban land uses in the study area. Ten parameters (pH, electrical conductivity, total dissolved solids, total hardness, calcium, magnesium, chloride, nitrate and sulfate) were determined using standard methods. The resulting water quality indices revealed that 58.09% of the samples were rated very poor while 21.73%, 9.08% and 11.1% were rated poor, good and excellent, respectively in rural land use. The analysis of samples drawn from urban land use revealed that 76.55% of the water was unfit for drinking while 14.4%, 6.42% and 2.63% were found to be very poor, good and excellent, respectively. pH, total dissolved solids, chloride, total hardness and nitrate were beyond the permissible limits for urban land use while, pH, total hardness and nitrate were above permissible limits for rural land use. These parameters were found to be responsible for the poor water quality rating in the study areas. The paper recommends a comprehensive effective sewerage system for safe disposal of sewage, efficient waste water handling and control of urban runoff to prevent groundwater quality deterioration in the study areas.

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