The Bowati in Kordofan, Sudan: Unique Aquatic Ecosystems of a Non-Nilotic In-Land Delta

This paper describes the unique in-land, non-Nilotic delta of Wadi El Galla, a seasonal water course which originates in the Nuba Mountains of Kordofan region and terminates in a chain of small ponds each known locally as a Bouta (pl Bowati). The Bowati are inhabited by a community of aquatic plants forming a wide spectrum ranging from small true (Euophytes) to large woody trees. The euophytes encountered were grouped into six categories. The free-floating species were represented by the small Lemna purpusilla Torr. and the larger Pistia stratiotes L. while only one submerged species was found: Ottelia alismoides (Planch.) Welp. One suspended species was found, Utricularia stellaris L. F. Three species of the floating-leaved plants were encountered namely, Nymphaea lotus L., N. micrantha Guill. & Perrott and Nymphoides nilotica (Kotschy & Peyr.) Léonard. The emergent Limnophyton obtusifolium (L.) Miq. was very prominent in all the Bowat constituting with N. lotus the two dominant species. Trailing from the Bouta edge and forming thick mats on the open water is Neptunia oleracea Lour., a member of the Fabaceae family. Within these euophytes and towering to over ten meters is the woody tree Mitragyna inermis Kuntze. Some of herbaceous plants are a source of food

two dominant species. Trailing from the Bouta edge and forming thick mats on the open water is Neptunia oleracea Lour., a member of the Fabaceae family. Within these euophytes and towering to over ten meters is the woody tree Mitragyna inermis Kuntze. Some of herbaceous plants are a source of food for the local community such as the bulbils of Nymphaea micrantha. These meagrely studied ecosystems are under threat from natural and anthropogenic factors. The former are the recurrent drought, climate change, and the latter are due to urbanization, overexploitation and oil activities. There is an urgent need for delineating and mapping the geomorphology, drainage patterns of Al Muglad in-land delta as well as the number and sites of the Bowati. The taxonomy of the aquatic species, their nutritive and medicinal values are other areas of research. Within such a context, a concerted national and international endeavour is called for to conserve these unique ecosystems and conceivably, declaring them as protected sites.

Introduction
The area of study is in the north western part of the Muglad Basin in West Kordofan State (Figure 1). The Muglad Basin is a large rift basin in Northern Africa. The basin is situated within southern Sudan and South Sudan, and it covers an area of approximately 120,000 square kilometres across the two nations. It contains several hydrocarbon accumulations of various sizes, the largest of which are the Heglig and Unity oil fields [1]. The Muglad basin is the largest known rift in the Sudan interior. It trends northwest-southeast and covers about 120,000 km 2 . The basin is around 800 km in length and 200 km in width [2]. Khor Abu Habil terminates in a delta in the White Nile. Khor Abu Habil has a common water shed with Wadi El Galla which flows southwest wards while Khor Abu Habil flows northeast wards. Wadi El Galla flows from the Nuba mountain near El Dilling town to the south west direction and terminates in Muglad town in the form of an inland delta constituted of a chain of small ponds each known locally as a Bouta (pl Bowati). This delta has not been previously recorded in the literature of the geology and geomorphology of the Republic of the Sudan. The delta comprises one of the unique, least studied aquatic ecosystems hosting a remarkable floral community.

Wadi El Galla Catchment
The catchment area of Wadi El Galla is dominated by the Basement Complex rocks. These rocks consist of igneous and metamorphic assemblage which is made up of folded gneiss and schist of sedimentary and volcanic origin with foliated granites. Synorogenic or late orogenic granite emplacement and basic and ultra-basic bodies also occur [3]. The formation unconformable overlies the Basement complex rocks. It is mainly composed of multi layers of sandstone and mudstone sediments of non-marine origin [3]. On the downstream part of Wadi El Galla, the Umm Rawaba formation appears. This formation is composed of ill-sorted fluvial continental deposits made up of sand, clay and gravel. It lies unconformable on the Nubian Sandstone formation [4].
The drainage system of Wadi El Galla is shown in Figure 2.  The area falls in a semi-humid tropical climate zone. The rainy season extends from May to October with peak values in August when the ITCZ is usually at its extreme northern position. The average mean maximum temperature over the area is 39.0˚C while minimum temperatures are in the range of 24.6˚C -26.1˚C in the cool months of January/February.

The Bowati of Wadi El Galla
Wadi El Galla flows sluggishly southward in a shallow valley skirting the edge of the sandy pediplain around AnNuoud town. The Wadi disperses in a delta ( Figure 3), known as Al Muglad (after the reddish sandy clay soil which predominates in the area). Within and around Al Muglad Wadi El Galla forms a chain of small ponds each known known locally as a Bouta (pl Bowati). These Bowati hold water for almost a year and are utilized by the locals as sources of water ( Figure 4). They also constitute a special ecosystem rich with aquatic plants ( Figure 5).    The rapid growth of duckweeds finds application in bioremediation of polluted waters, in municipal wastewater treatment [9] and as test organisms for environmental studies.

Suspended
Lentibulariaceae: The Bladderworts belong to the most recently evolved group of carnivorous plants. Within the Bowati Utricularia stellaris L.f. was encountered suspended within the water. It was distinguished with its yellow flowers and solitary traps for capturing small organisms ( Figure 9).

Emergent
Within this group of macrophytes two species were encountered belonging to two different families: Alismataceae: This family is represented by Limnophyton obtusifolium (L.) Miq. (Figure   15), growing in dense clusters among the other floating and emergent plants. Poaceae: The Poaceae family was represented by the perennial wild rice Oryza longistaminata A. Chev. & Roehrich (Figure 16).

Trailing on Water Surface
Two species of two different families were encountered within the Muglad Bowati, namely Ipomoea aquatica Forssk. and Neptunia oleracea Lour. The former belongs to the family Convolvulaceae while the other belongs to the family Fabaceae. Unlike I. aquatica which is a common herb in most aquatic habitats in Sudan, N. Oleracea, known as water mimosa, is rarely reported in the literature.
It was found growing prostrate and floating on the water in several Muglad Bowati ( Figure 17) sometimes forming a wide mat in open surfaces ( Figure 18). The trailing stem produces spongy, fibrous roots between the nodes, while the inflorescence, a solitary axillary spike, erects over the water surface ( Figure 19).     The fruit is a legume, green when unripe and brown when mature, splitting along both sides. Pteridophyte: ferns Marsileaceae: Marsilea gibba A. Braun: Rooted, aquatic herb with floating leaves ( Figure   20).

Discussion
The inland delta of Wadi El Galla is a remarkable formation from both geomorphological and biological aspects. It is acclaimed as being, so far, the only non-Nilotic inland delta in Sudan. And as such, it is least mentioned and studied. The seasonal ponds (Bowati) within this delta portray a unique cluster of  aquatic ecosystems, rich in aquatic macrophytes. Twelve species were reported belonging to ten families. However, with time and accessibility constraints, this list is not inclusive and other species are most probably had been overlooked. This information in this article is a significant contribution to previous, meagre studies on freshwater aquatic macrophytes [10]. The Muglad Bowati ecosystems are under threat from both natural and anthropogenic factors. The former is the recurrent drought and climate change, while the latter is due to oil activities, urbanization, and overexploitation. The repercussions of the anthropogenic factors on these unique wetlands are imminent.

Recommendations
The following measures are recommended: 1) Geological, geomorphological as well as hydrological investigations are required to study Al Muglad in-land delta.
2) A clear national vision towards the aquatic habitats in the Sudan needs to be developed.
3) Detailed limnological studies are needed for the biotic and abiotic features of Al Muglad Bowati. 4) Collaboration between Sudan and the regional and international organizations and institutions such as the Royal Botanic Gardens, Kew, IUCN and IHE will be a great asset.
5) It is proposed that Al Muglad in-land delta and its Bowati systems to be declared as protected sites.

Conclusions
Wadi El Galla is a seasonal water course originating in the Nuba Mountains of Kordofan region and terminates in an inland delta forming a chain of small ponds each locally known as a Bouta (pl Bowati). The Bowati are inhabited by a community of aquatic plants embracing six growth forms: free-floating, submerged, suspended, floating-leaved, emergent and trailing from the Bouta edge. Some of herbaceous plants are a source of food for the local community such as the bulbils of Nymphaea micrantha.
These meagrely studied ecosystems are under threat from natural and anthropogenic factors. The former are the recurrent drought, climate change, and the latter are urbanization, overexploitation, and oil activities.
There is a need for detailed geomorphological and hydrological studies of Al Muglad in-land delta. Detailed limnological studies are also needed for the biotic and abiotic features of Al Muglad Bowati.