The Black Valley (Wied is-Sewda)

This is a study as part of the GLOBE Water Bodies Challenge 2021. St. Michael School, a boys' secondary school, is situated in Santa Venera and has been an active GLOBE school for the past 2 years.

A valley, in maltese wied and in arabic wadi can be conveniently defined as a depression of the land surface formed as a result of erosion mostly by the passage of water or land movements and usually containing running water during some time of the year. The depth, width and length of valleys strengthen these hypotheses. The catchment causes a watercourse of a valley. The catchment area or drainage basin is an area made of ridges and land at a higher level. This serves as a natural basin where rainfall and consequently runoff is directed to the watercourse which is basically a water channel along which there is movement of water in the form of a stream or river. In fact watercourse can be defined as a natural or man-made open channel on the land surface through or along which water may flow". There are about 100km of of main watercourse in Malta and about double that amount in minor tributaries. Most of the Maltese valleys are appropriately called river valleys because of watercourses actively occurred a long period of time. Different influences have reduced water flow, but the rivers have left behind the legacy of life, both natural and artificial, that water always generates. This is why valleys remain a very important part of Malta's natural, social and cultural history. The sloping sides have led to agricultural activities, the watercourse to very fertile land supporting ecological systems, which all combined, have resulted in a characteristic landscape particular to our islands.

The importance of valleys can be summarised as below: 1. They are habitats of great ecological value due to the amount of flora and fauna they support, sometimes finding rare and endangered and indigenous species. 2. They are important water resources where aquifer replenishment is enhanced. 3. Their channel or watercourse along which water is carried prevents flooding over flat land. 4. Valleys enable storage of water temporarily or permanently to be used for agriculture. 5. They collect eroded soil. 6. They usually possess cultural, historical and archaeological heritage. 7. They have a recreational value for tourism and locals alike. 8. They have beautiful aesthetic values. These valuable assets have been exploited completely by human activities which has led to negative influence and sometimes resulted in undesired effects which are detrimental to public health either directly or indirectly and thus pose concern.

When translated, the name could mean the Valley of the Black Woman. Locals point the fact that the valley's name originated from a certain dark coloured woman who lived in the valley many years ago. The legend that the woman used to serve as a spy for the Turkish pirates who used to come into the valley with boats from Marsa creeks, to capture Maltese and take them as slaves. Ultimately she was caught and burnt to death in Rabat. No other information is found on this regard, but certain other sources stated the name came from a Chapel in the valley. 

In the 18th century many valleys including Wied is-Sewda, contained marsh and standing waters even in summer, and this was a health hazard. As illnesses increased "there were repeated nineteenth-century prohibitions from irrigating vegetables in the upper Sewda valley, behind Mdina, particularly after June .... Drainage was slowly carried out to give dry land and free flowing water so improving public health." (SM Haslam and J Borg, The River Valleys of the Maltese Islands, page 28). Sewage dumping into Wied is-Sewda to the detriment of public health was also common in the 1850s. Mr Chadwick reported that in the 1890s Mount Carmel Hospital in Attard used to use the watercourse for waste disposal. "The persistent Maltese view that rivers are for waste, and that the waste can disappear, implies much waste was put in earlier and that therefore much water was there to convey it away." (SM Haslam and J Borg, The River Valleys of the Maltese Islands, page 119). This mentality is easily recognised in the numerous activities practised in the valley up to the present day which have to be investigated thoroughly to understand the total human influence, and the effects arising from this 17 influence. The activities or measures and processes which are found in the valley include: • Agricultural • Industrial • Recreational These activities and processes have some sort of impact on environmental health and can offer different potential dangers to the individuals practising the activities as well as the community as a whole. 

A Walk along this Valley ....

This valley as said before is divided in rural and urban area. Walking in the rural area there are fields, and different water basins (Dam like) for collecting water and used mainly for irrigation of adjacent fields. The valley has a pumping station and also different farms. This time of the year different trees bloom. Other Endemic trees noted are Cypress trees, Olive Trees and Carob Trees. Unfortunately one can notice two alien trees which are invasive and taking over endemic trees and vegetation. These are the Acacia Tree and the Castor Oil Tree

Human Impact on the valley .....

Unfortunately the human impact on this valley is visible. Apart from heavy vehicles parked in different areas, one can notice rubbish thrown illegal

What did we studied as part of the Water Bodies Challenge?

During the holidays, following COVID restrictions limiting the participants to a minimum of 2 persons, we collected water samples from 2 different areas. Unfortunately, most of the water has dried up except from specific spot. We managed to collect some water samples for analysis. For this challenge, we tested the pH and nitrates level in the two samples. Adjacent to the valley basin, in which rainwater collects, one can find farms and fields. Through our observations we will test if these land-uses are effecting the nitrate and pH level.

Laboratory testing on water collected

We tested the pH and Nitrates level. For pH we used the Einstein Tablet 3 with a dedicated pH sensor. For the nitrates we used a Nitrate testing kit.

Results:

pH of water of Area 1 was: 6.882

pH of water Area 2 was: 7.12

Nitrates in water Area 1: Over 50mg/l

Nitrates in water Area 2: 3mg/l

Results Interpretation:

When observing the pH and nitrates of both areas studied we noted that the pH and nitrate level vary for Area 1 (located near fields and farm) and Area 2 (near the picnic area). High nitrates will lower pH. Few days ago there was drainage over flowing due to a fault in Area 1. This situation made things worst.

What's next:

For next year as the GLOBE team at St. Michael School will investigate in more detail this valley by carrying out more water tests from other selected areas along the valley, make tree height measurements using GLOBE Observer App and other GLOBE observations using the GLOBE Atmosphere and Hydrosphere Protocols. The report of our investigation will be presented to Attard and Qormi Local Council, 2 localities which are drained by the valley.