**3.4 Seasonal changes in water chemistry**

## *3.4.1 Khalong-la-Lithunya and Ha-Matela*

Mean nutrient concentrations in *Khalong-la-Lithunya* and Ha-Matela wetlands runoff-water are presented in **Tables 6** and **7**. There were significant differences


*Wetland Health in Two Agro-Ecological Zones of Lesotho: Soil Physico-Chemical Properties… DOI: http://dx.doi.org/10.5772/intechopen.101836*

*Ca = calcium, Mg = magnesium, K=potassium, Na = sodium; means with the same letter in one column are not significant at 5% Duncan multiple range test (DMRT).*

#### **Table 6.**

*Nutrient concentrations in water for* Khalong-la-Lithunya *wetland.*


*Ca = calcium, Mg = magnesium, K=potassium, Na = sodium, means with the same letter in one column are not significant at 5% Duncan multiple range test (DMRT).*

#### **Table 7.**

*Mean selected water chemical properties for* Ha-Matela *wetland transects.*


#### **Table 8.**

*Burden of N and P in various eutrophicated water.*


#### **Table 9.**

*Criteria for surface water quality for lakes and reservoir.*

within and across sites. Generally, higher base cations (K, Ca, Mg and Na) could be observed in the KHL compared to the HM wetlands. The total P and total N in both wetlands were very high when compared with the values provided in **Table 8** [48–50]. Both wetlands could be classified as hypertrophic in terms of TN and TP contents (**Table 8**). The surface water quality according to CENPA [51] could be classified in class II (**Table 9**). High N and P in surface water of wetlands is a wellrecognized cause of the level of degradation [4, 52]. Th**is** author asserted that much of this N and P delivery is the consequence of changing land use. Omernik et al. [53] compared 175 small watersheds differing in land use and lacking point source inputs. These authors demonstrated that a strong correlation of N and P concentrations occurs with a fraction of land in agriculture. In a related study, Johnson et al. [54] found that in small sub-watersheds of the Saginaw Basin, land use explained over half of the variation in nitrate and TN. In Southern Africa, the threshold of TP in freshwater was estimated to be 0.73 mg/L. However, close observation of **Tables 8** and **9** compared with **Tables 6** and **7** indicated that the water quality of Lesotho's wetlands are excessively enriched and are considered to be highly eutrophic. Eutrophication is generally indicated by accumulation of metabolic products (e.g. hydrogen sulphide in deep waters), discolorations or turbidity of water (resulting in low or poor light penetration), deterioration in the taste of water, depletion of dissolved oxygen and an enhanced occurrence of cyanobacterial bloom-forming species as shown on **Tables 6** and **7** [55, 56].

#### **3.5 Nitrogen and carbon isotopic signatures**

The vegetation 15N and 13C isotopic signatures for KHL and HM wetlands are presented in **Table 10**. The result indicates that δ13C in KHL wetland was higher, indicated by more negative values, compared to that in HM wetland. This shows that the KHL wetland is less degraded compared to HM wetland. Furthermore, results showed that less N is lost in KHL wetlands compared to that at HM. These *Wetland Health in Two Agro-Ecological Zones of Lesotho: Soil Physico-Chemical Properties… DOI: http://dx.doi.org/10.5772/intechopen.101836*


#### **Table 10.**

*Isotopic signatures of δ13C and δ15N in two wetlands sites.*

may be attributed to high overgrazing and over-cultivation observed at HM as opposed to KHL wetland which is now under conservation. A breakdown of the δ13C and δ15N within both sites across the toposequence (**Table 10**) showed that there is higher δ13C in the minimally degraded wetland (KHL) compared with that from HM. Furthermore, the results of the breakdown also showed that less δ15N is lost from KHL compared to the HM [23, 57, 58]. The variation in the δ13C across sites can be ascribed to differences in vegetation species. The increased δ15N in plants is often interpreted as an indicator of sewage or pollution [59, 60]. The HM wetland is still being used for human activities (i.e. livestock grazing and watering and cropping especially maize and sorghum). Therefore, higher δ15N in the vegetation samples (i.e. 2.00–6.18‰) may as a result of build-up of pollutants. It could be observed that higher δ15N (i.e. 6.18‰) was observed in the lower slopes/wetlands compared to other section of the toposequence.

### **4. Conclusion and recommendations**

Results of the study showed that higher base cations were observed in the soils and water samples of the KHL wetlands compared to that of the HM wetlands. Also, the results of the isotopic signatures of were significantly higher (i.e. δ13C and δ15N) in HM wetlands (shown by less negative and high positive values) compared to the KHL wetlands. The result indicated that δ13C in KHL wetland was higher, indicated by more negative values, compared to that in HM wetland suggesting that the former wetland is less degraded compared to the latter confirming that if other wetlands in the country will revert to their original status if conserved/rehabilitated. Results also showed that both wetlands have higher levels of total N and total P in run-off water samples suggesting that both wetlands can be classified as hypertrophic. However, higher base cations in the soils and water samples of the KHL wetlands may be related more to the geology of the site as this has been under conservation for about 6 years. Avoiding the restoration of agricultural land with high nutrient levels in favor of land with lower amounts of nutrients may increase the likelihood of restoration success.

### **Acknowledgements**

Sincere thanks go to the Regional University Forum (RUFORUM), Uganda that awarded grants RU 2009/GRG15 to the two M.Sc. students—Mr. Nkheloane and

Ms. Mating. Also, thanks go to the International Atomic Energy Agency (IAEA), Vienna, Austria that provided N-15 isotope fertilizer and analyzed the data under the grant agreement CRP 15399/R1-3.
