# Comparison of Well and Polluted Dam Waters: Impacts on Biodiversity and Agriculture in Mayo-Tsanaga, Sahelian Mountainous Zone of Cameroon

Alexis Dzokom, Ezechiel Kodji, Roger Djouldé Darman

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Alexis Dzokom, Ezechiel Kodji, Roger Djouldé Darman. Comparison of Well and Polluted Dam Waters: Impacts on Biodiversity and Agriculture in Mayo-Tsanaga, Sahelian Mountainous Zone of Cameroon. Sahel Nature Consulting Revue, 2025, Clean Water, 9 (9), pp.1-13. [hal-05007707](https://hal.science/hal-05007707v1)

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# Comparison of Well and Polluted Dam Waters: Impacts on Biodiversity and Agriculture in Mayo-Tsanaga, Sahelian Mountainous Zone of Cameroon

Alexis DZOKOM<fnref n="1" />,<fnref n="2" />, Ezéchiel KODJI<fnref n="3" />, Roger DJOULDÉ DARMAN<fnref n="3" />

## Abstract

The use of glyphosates in intensive agriculture has raised concerns regarding their effects on water quality, biodiversity, and the safety of agricultural products. This study compares the water quality of irrigation wells to that of reservoirs located near agricultural fields where glyphosates are commonly used. The analysis focused on the physicochemical and biological parameters of the water, as well as their effects on aquatic biodiversity and the quality of fruits and vegetables produced. The results indicate that reservoir waters exhibit more pronounced acidification (mean pH = 5.8 ± 0.3) compared to well waters (mean pH = 6.7 ± 0.2). Glyphosate and its primary metabolite, aminomethylphosphonic acid (AMPA), were found at significantly higher concentrations in reservoirs (glyphosate: 35 ± 5 µg/L; AMPA: 12 ± 2 µg/L) than in wells (glyphosate: 5 ± 1 µg/L; AMPA: 2 ± 0.5 µg/L). The high presence of cyanobacteria (*Microcystis* spp.) in reservoirs (density: 500,000 cells/mL) indicates excessive nutrient enrichment (nitrates and phosphates), promoting eutrophication. The average fruit weight decreased from 180 g to 110 g, suggesting slowed growth under environmental stress. Further research could deepen the understanding of glyphosate's impact on human health in this specific region and assess the effectiveness of alternative techniques for restoring water quality and biodiversity.

**Keywords:** Glyphosate, water quality, biodiversity, irrigation, agricultural pollution, Mayo-Tsanaga

## Introduction

Water is an essential resource for agriculture, particularly in Sahelian regions where access to quality water is a major challenge. The pollution of irrigation water by phytosanitary substances, especially glyphosates, raises serious concerns about its impact on biodiversity and the quality of agricultural production. The Mayo-Tsanaga, a mountainous Sahelian region in Cameroon, faces increasing herbicide use to maximize agricultural yields, leading to risks of water contamination, particularly in reservoirs and irrigation wells.

The comparative study of the water quality from irrigation wells and reservoirs polluted with glyphosates allows for an assessment of the effects of this pollution on the water cycle, aquatic biodiversity, and the quality of fruits and vegetables produced. According to Mathews et al. (2020),

herbicides, particularly glyphosates, can persist in the environment and accumulate in soils and surface waters, thereby affecting aquatic flora and fauna. Moreover, their infiltration into groundwater can compromise the quality of water used for irrigation, with potential consequences for human health (Giesy et al., 2000; Folefack & Djouldé, 2013).

The dynamics of the water cycle in a Sahelian region like Mayo-Tsanaga are particularly sensitive to agricultural pollution due to low rainfall and a high dependency on surface and groundwater for irrigation. Additionally, the presence of glyphosates in irrigation water can alter the physiology of cultivated plants, affecting their growth and nutritional value (Benbrook, 2019; Djouldé, 2007; Djouldé, 2006). Furthermore, water contamination can lead to a decline in aquatic biodiversity,

<footnote n="1">¹SAHEL NATURE CONSULTING</footnote>

<footnote n="2">²Department of Geography, Faculty of Arts Letters and Social Sciences, University of Maroua, Cameroon</footnote>

<footnote n="3">³Department of Environmental Science, National Advanced School of University of Maroua, University of Maroua, Cameroon</footnote>

<footnote n="3">³Department of Agriculture Animal Husbandry and By-Products, Faculty of Sciences, University of Garoua, Cameroon</footnote>
particularly by eliminating species that are sensitive to herbicides (Mamy et al., 2010; Dzokom, 2023; Dzokom et al., 2024a,b). This study aims to compare the physicochemical and biological characteristics of well and reservoir waters in relation to their agricultural use and to analyze their impacts on the quality of plant production. It contributes to the assessment of environmental and health risks associated with glyphosate use in Mayo-Tsanaga and proposes alternatives for sustainable water resource management in this Sahelian region.

## Materials and Methods

The comparative study of the water quality from irrigation wells and reservoirs polluted

with glyphosates in Mayo-Tsanaga is based on a multidisciplinary methodological approach combining physicochemical, biological, and agronomic analyses. This approach aims to evaluate the impact of pollution on the water cycle, aquatic biodiversity, and the quality of fruits and vegetables produced in this mountainous Sahelian zone.

### 1. Study Site

Mayo-Tsanaga is located in the Far North Region of Cameroon, characterized by a Sahelian climate with low rainfall (400 to 800 mm/year) and a high dependency on surface and groundwater resources for agriculture (Seiny-Boukar & Temple, 2009).

<figure><img src="image_2.png" /><figcaption>Figure 1: Study Area</figcaption></figure>

The main water sources for irrigation in this region include groundwater wells and artificial reservoirs, which are often exposed to agricultural pesticides, particularly glyphosates used for weed control.

### 2. Water Sampling

Sampling was conducted at ten sites, categorized as follows:

* Five irrigation wells located near vegetable farms, mainly used during the dry season.

* Five artificial reservoirs receiving runoff water from agricultural plots treated with glyphosates.

Water samples were collected following the protocol of the U.S. Environmental Protection Agency (USEPA, 2007) using pre-sterilized polyethylene bottles. Each sample was filtered on-site using 0.45 µm filters for the analysis of physicochemical and biological parameters.

### 3. Physicochemical Water Analysis
The analyses focused on the following parameters:

* **pH and electrical conductivity,** measured in situ with a multiparameter probe (Hanna Instruments, USA).

* **Turbidity,** analyzed with a HACH 2100P turbidimeter.

* **Glyphosate and metabolites (AMPA),** determined by high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) following the method of Kolpin et al. (2006).

* **Nitrate and phosphate concentrations,** measured by UV-visible spectrophotometry (APHA, 2017).

* **Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD₅),** assessed according to the standardized ISO 5815-1 (2019) method.

## 4. Aquatic Biodiversity Assessment

The impact of pollution on biodiversity was evaluated by characterizing the aquatic fauna and flora at different sites:

* **Normalized Global Biological Index (IBGN) (AFNOR, 2016),** based on the identification of macroinvertebrates as water quality indicators (Oligochaetes, Ephemeroptera, Trichoptera).

* **Presence of phytoplankton and cyanobacteria,** analyzed using optical microscopy and counted in a Neubauer chamber (Legendre & Legendre, 2012).

## 5. Quality of Produced Fruits and Vegetables

Samples of fruits and vegetables (tomatoes, lettuce, and onions) cultivated with these waters were collected from the same sites and analyzed based on the following criteria:

* **Glyphosate and pesticide residue content,** determined by HPLC-MS (EFSA, 2021).

* **Nitrate content,** assessed by colorimetry according to the method of Cataldo et al. (1975).

* **Nutritional parameters (vitamins, sugars, and minerals),** measured by infrared spectroscopy and ion chromatography (FAO, 2018).

## 6. Statistical Data Analysis

The results were processed using R software (R Core Team, 2020) and analyzed through:

* **Analysis of Variance (ANOVA)** for physicochemical parameters.

* **Principal Component Analysis (PCA)** to evaluate correlations between water pollution, biodiversity, and agricultural production quality.

This rigorous methodology enables the assessment of the environmental and health impacts of irrigation water in Mayo-Tsanaga, providing essential comparative data for better water resource management in the Sahelian zone.

## Results and Discussion

The analysis of irrigation water from wells and reservoirs in Mayo-Tsanaga revealed significant differences in physicochemical and biological quality, with notable impacts on aquatic biodiversity and agricultural production quality.

### 1. Physicochemical Water Quality

#### 1.1. Acidity and Conductivity

The lower pH in polluted reservoirs (5.8) suggests acidification due to chemical residues (Borggaard et al., 2019). The high conductivity (950 µS/cm) of reservoir water reflects a strong dissolved salt load, likely resulting from pesticide and fertilizer inputs (WHO, 2021).
## 1.2. Nitrate and Phosphate Contamination

The high nitrate content (45.6 mg/L) in reservoir water exceeds agricultural pollution thresholds and serves as an indicator of eutrophication (Smith &

Schindler, 2009). Phosphate concentrations (3.5 mg/L) are significantly high, promoting toxic algal growth and oxygen depletion (Paerl et al., 2016).

The following table details the physicochemical quality of the water.

<table><caption>Table 1: Physicochemical Parameters of Analyzed Water</caption><thead><tr><td>Parameters</td><td>Irrigation Wells</td><td>Reservoirs Polluted with Glyphosates</td><td>WHO Drinking Water Standards</td></tr></thead><tbody><tr><td>pH</td><td>7.2 ± 0.3</td><td>5.8 ± 0.5</td><td>6.5 - 8.5</td></tr><tr><td>Conductivity (µS/cm)</td><td>520 ± 40</td><td>950 ± 70</td><td>&lt; 1000</td></tr><tr><td>TDS (mg/L)</td><td>310 ± 25</td><td>600 ± 50</td><td>&lt; 500</td></tr><tr><td>Nitrates (NO<sub>3</sub><sup>-</sup>) (mg/L)</td><td>12.4 ± 2.1</td><td>45.6 ± 5.4</td><td>&lt; 50</td></tr><tr><td>Phosphates (PO<sub>4</sub><sup>3-</sup>) (mg/L)</td><td>0.8 ± 0.2</td><td>3.5 ± 0.6</td><td>&lt; 5</td></tr><tr><td>Glyphosate (µg/L)</td><td>ND</td><td>180 ± 20</td><td>&lt; 700</td></tr><tr><td>Dissolved Oxygen (mg/L)</td><td>7.5 ± 0.6</td><td>4.2 ± 0.8</td><td>&gt; 5</td></tr><tr><td>BOD<sub>5</sub> (mg O<sub>2</sub>/L)</td><td>3.2 ± 0.5</td><td>7.8 ± 1.2</td><td>&lt; 6</td></tr><tr><td>COD (mg O<sub>2</sub>/L)</td><td>15.2 ± 2.3</td><td>40.5 ± 4.7</td><td>&lt; 30</td></tr><tr><td>Heavy Metals (Cd, Pb, As) (µg/L)</td><td>ND</td><td>Detected Presence</td><td>Variable depending on metal</td></tr></tbody></table>

ND = Not Detected

## 1.3. Presence of Glyphosate

Glyphosate reaches 180 µg/L in the reservoirs, confirming contamination due to intensive agricultural practices (Benbrook, 2019). This pesticide is associated with impacts on both aquatic and terrestrial biodiversity (Giesy et al., 2000).

## 1.4. Oxygenation Parameters and Organic Matter

Dissolved oxygen levels in the reservoirs (4.2 mg/L) are critically low, leading to anoxic conditions that affect aquatic fauna (Dodds et al., 2019). The high BOD<sub>5</sub> (7.8 mg O<sub>2</sub>/L) and COD (40.5 mg O<sub>2</sub>/L) values indicate significant organic pollution, typical of water receiving agricultural and industrial waste (Reddy & DeLaune, 2008).

## 1.5. Heavy Metals

The detected presence of cadmium, lead, and arsenic in the reservoirs is concerning, as these elements have toxic effects on human health and ecosystems (Jaishankar et al., 2014).

## 1.6. Ecological and Health Impacts

* **Affected Aquatic Biodiversity:** Acidification, reduced dissolved oxygen, and chemical pollution decrease species diversity (Camargo & Alonso, 2006).

* **Impacts on Fruit and Vegetable Quality:** The absorption of glyphosate and heavy metals by crops poses health risks (Bai et al., 2016).

* **Human Health Risks:** Consumption of contaminated water may cause gastrointestinal diseases and neurological disorders (WHO, 2021).

## 1.7. General Parameters (pH, Conductivity, Turbidity)

The results indicate that reservoir waters exhibit more pronounced acidification (mean pH = 5.8 ± 0.3) compared to well water (mean pH = 6.7 ± 0.2). According to Giesy et al. (2000), the acidification of surface waters is a well-known effect of organic pollutants such as glyphosates,
which promote the production of organic
acids during their degradation.

Electrical conductivity is also higher in reservoir waters (750 ± 50 µS/cm) compared to wells (420 ± 30 µS/cm), indicating a higher ionic load due to the presence of pesticide residues and nutrients from agricultural runoff (Mathews et al., 2020).

**1.8. Contamination by Glyphosate and Metabolites**

Analyses of glyphosate and its main
metabolite, aminomethylphosphonic acid
(AMPA), reveal significantly higher
concentrations in reservoirs (glyphosate: 35
± 5 µg/L; AMPA: 12 ± 2 µg/L) than in wells
(glyphosate: 5 ± 1 µg/L; AMPA: 2 ± 0.5
µg/L). These levels exceed WHO drinking
water recommendations (< 0.1 µg/L) and
could affect human health and the
environment (Benbrook, 2019).

This accumulation in surface waters is
attributed to the runoff of pesticide residues
applied to upstream agricultural fields.
Studies by Kolpin et al. (2006) have
demonstrated that glyphosate has a strong
affinity for soil particles but can be
transported into water bodies through
precipitation and erosion.

**2. Impact on Aquatic Biodiversity**

**2.1. Loss of Biodiversity and Ecological Imbalance**

Species richness decreases from 28 species
in wells to 12 species in polluted reservoirs,

indicating a significant loss of diversity
(Dodds et al., 2019; Dzokom, 2025).

<figure><img src="image_3.png" /><figcaption>**Photo 1:** a) *Chironomus plumosus* and b) *Limnephilus flavicornis*</figcaption></figure>

The Shannon index drops to 1.3 in reservoirs, indicating a community dominated by a few resistant species, a sign of severe pollution (Magurran, 2004; Dzokom, 2025). The Simpson index at 0.42 shows a high dominance of a few opportunistic taxa at the expense of balanced diversity (Chapin et al., 2000; Dzokom, 2025).

**2.2. Reduction of Indicator Macroinvertebrates for Good Water Quality**

The percentage of Ephemeroptera, Plecoptera, and Trichoptera (EPT) falls to 15%, whereas it exceeds 50% in wells, confirming the ecological degradation of reservoirs (Bonada et al., 2006). Resistant macroinvertebrates such as chironomids and oligochaetes are overrepresented, indicating organic and chemical pollution (Merritt & Cummins, 2008; Dzokom, 2024b,c).

<table><caption>Tableau 2: Impact du glyphosate sur la biodiversité aquatique</caption>
   <thead>
    <tr>
     <td>
      Paramètres biologiques
     </td>
     <td>
      Puits d'irrigation
     </td>
     <td>
      Barrages pollués aux glyphosates
     </td>
     <td>
      Seuils de perturbation écologique
     </td>
    </tr>
   </thead>
   <tbody>
    <tr>
     <td>
      Richesse spécifique (Nombre d'espèces)
     </td>
     <td>
      28 ± 3
     </td>
     <td>
      12 ± 2
     </td>
     <td>
      &gt; 20 (bonne biodiversité)
     </td>
    </tr>
    <tr>
     <td>
      Indice de Shannon (H')
     </td>
     <td>
      2,85 ± 0,15
     </td>
     <td>
      1,30 ± 0,20
     </td>
     <td>
      &gt; 2 (bonne diversité)
     </td>
    </tr>
    <tr>
     <td>
      Indice de Simpson (D)
     </td>
     <td>
      0,78 ± 0,05
     </td>
     <td>
      0,42 ± 0,07
     </td>
     <td>
      &gt; 0,6 (faible dominance)
     </td>
    </tr>
    <tr>
     <td>
      Macroinvertébrés indicateurs de bonne qualité (EPT %)
     </td>
     <td>
      58 ± 5
     </td>
     <td>
      15 ± 4
     </td>
     <td>
      &gt; 50% (milieu sain)
     </td>
    </tr>
    <tr>
     <td>
      Densité de phytoplancton (cellules/mL)
     </td>
     <td>
      3500 ± 400
     </td>
     <td>
      8700 ± 900
     </td>
     <td>
      &lt; 5000 (pas d'eutrophisation)
     </td>
    </tr>
   </tbody>
  </table>
<table><tr><td>Biomasse des cyanobactéries toxiques (µg/L)</td><td>ND</td><td>680 ± 75</td><td>&lt; 100 (risque sanitaire)</td></tr><tr><td>Abondance des poissons (individus/m³)</td><td>3,2 ± 0,4</td><td>0,8 ± 0,3</td><td>&gt; 2 (bonne population piscicole)</td></tr><tr><td>Taux de malformations chez les poissons (%)</td><td>2,1 ± 0,5</td><td>14,5 ± 2,3</td><td>&lt; 5% (milieu peu pollué)</td></tr></table>

## 2.3. Proliferation of Toxic Cyanobacteria and Eutrophication

The density of phytoplankton doubles in the reservoirs (8,700 cells/mL), suggesting eutrophication due to phosphate and nitrate inputs (Paerl & Otten, 2016). The biomass of toxic cyanobacteria reaches 680 µg/L, well above the risk threshold for aquatic fauna and human health (Carmichael, 2001). These cyanotoxins affect fish and macroinvertebrates, disrupting the aquatic food chain (Paerl & Paul, 2012).

## 2.4. Collapse of Fish Populations and Morphological Anomalies

Fish abundance drops from 3.2 to 0.8 individuals/m³ in polluted reservoirs, indicating a drastic reduction in available habitat (Dudgeon et al., 2006; Dzokom, 2025). The malformation rate reaches 14.5% in reservoirs, suggesting chronic exposure to pesticides and heavy metals (Cohen et al., 2009). Affected fish exhibit deformities in gills, the spinal column, and fins, attributed to glyphosate toxicity and eutrophication (Nagai et al., 2012).

## 2.5. Ecological and Health Impacts

* **Loss of aquatic biodiversity:** Weakening of aquatic ecosystems and disruption of food webs (Dudgeon et al., 2006; Dzokom, 2025).

* **Eutrophication and toxicity:** Proliferation of harmful algae threatening aquatic organisms and water consumers (Paerl & Otten, 2016; Dzokom, 2023).

* **Risks to fishing and local food supply:** Decline in fish stocks and contamination of fish with bioaccumulated toxins (Bai et al., 2016).

The assessment of aquatic biodiversity highlights a significant reduction in macroinvertebrate diversity in reservoirs compared to wells.

* **Normalized Global Biological Index (IBGN):**

* Wells: 15 ± 2 (good water quality)

* Reservoirs: 6 ± 1 (polluted water)

Reservoir sites show a strong decline in Trichoptera and Ephemeroptera populations, which are indicators of good water quality, replaced by Oligochaetes and Chironomids, which are tolerant to pollutants (Mamy et al., 2010).

Moreover, the high presence of cyanobacteria (*Microcystis* spp.) in reservoirs (density: 500,000 cells/mL) indicates excessive nutrient enrichment (nitrates and phosphates), promoting eutrophication. This phenomenon may be exacerbated by intensive herbicide use, which alters microbial balance and reduces dissolved oxygen availability (Solomon et al., 2016).

## 3. Impact on the Quality of Produced Fruits and Vegetables

### 3.1. Contamination by Glyphosate and Pesticide Residues

Fruits and vegetables irrigated with reservoir water contain 320 µg/kg of glyphosate, exceeding the 200 µg/kg limit recommended by the Codex Alimentarius (Benbrook, 2019). The total pesticide load (135 µg/kg) in crops watered with reservoir water is concerning, as it surpasses the European limit of 100 µg/kg (Bai & Ogbourne, 2016).
## 3.2. Excessive Accumulation of Nitrates and Phosphates

Nitrate content reaches 185 mg/kg in vegetables irrigated with reservoir water, dangerously approaching the 250 mg/kg limit set by WHO and the EU (Santamaria, 2006). Excess nitrates promote the formation of nitrosamines, known carcinogens (Lairon, 2010; Dzokom et al., 2024a,b).

<table><caption>Table 3: Impact of Water Quality on Fruits and Vegetables</caption><thead><tr><td>Quality Parameters</td><td>Fruits and Vegetables Irrigated with Well Water</td><td>Fruits and Vegetables Irrigated with Reservoir Water Polluted with Glyphosates</td><td>Standards and Quality Thresholds</td></tr></thead><tbody><tr><td>Glyphosate content (µg/kg)</td><td>ND</td><td>320 ± 25</td><td>&lt; 200 µg/kg (Codex Alimentarius)</td></tr><tr><td>Nitrate content (mg/kg)</td><td>55 ± 8</td><td>185 ± 15</td><td>&lt; 250 mg/kg (EU, WHO)</td></tr><tr><td>Phosphate content (mg/kg)</td><td>15 ± 2</td><td>48 ± 6</td><td>-</td></tr><tr><td>Heavy metals (Pb, Cd, As) (µg/kg)</td><td>Pb: 5 ± 1, Cd: 0.8 ± 0.2, As: ND</td><td>Pb: 45 ± 5, Cd: 5.2 ± 0.8, As: 12 ± 2</td><td>Pb &lt; 30, Cd &lt; 2, As &lt; 10 (EU, WHO)</td></tr><tr><td>Pesticide residue content (Σ pesticides, µg/kg)</td><td>22 ± 4</td><td>135 ± 10</td><td>&lt; 100 µg/kg (EU)</td></tr><tr><td>Vitamin C content (mg/100g)</td><td>52 ± 6</td><td>28 ± 5</td><td>-</td></tr><tr><td>Polyphenol content (mg/kg)</td><td>320 ± 20</td><td>150 ± 15</td><td>-</td></tr><tr><td>Total sugar content (g/100g)</td><td>7.2 ± 0.5</td><td>4.1 ± 0.6</td><td>-</td></tr><tr><td>Average fruit weight (g)</td><td>180 ± 10</td><td>110 ± 12</td><td>-</td></tr><tr><td>Vegetable firmness index (N)</td><td>6.5 ± 0.8</td><td>3.2 ± 0.6</td><td>-</td></tr><tr><td>Percentage of deformed fruits/vegetables (%)</td><td>3.5 ± 1.0</td><td>18.7 ± 2.4</td><td>&lt; 5% (commercial standard)</td></tr></tbody></table>

## 3.4. Deterioration of Nutritional Quality

Vitamin C content significantly decreases (28 mg/100g vs. 52 mg/100g in well water), indicating oxidative stress in plants exposed to pollution (Pérez-Jiménez et al., 2010). Polyphenol concentration is reduced by half (150 mg/kg vs. 320 mg/kg), affecting antioxidant properties and health benefits (Scalbert et al., 2005). The reduction in total sugars (4.1 g/100g vs. 7.2 g/100g) reflects an alteration in plant metabolism, linked to abiotic stress caused by contaminants (Delgado et al., 2013).

## 3.3. Heavy Metal Contamination

The worrying presence of lead (45 µg/kg), cadmium (5.2 µg/kg), and arsenic (12 µg/kg) in fruits and vegetables exposed to polluted water exceeds safety thresholds for human consumption (Jaishankar et al., 2014; Dzokom, 2023). The accumulation of these metals is linked to agricultural effluents and pesticides containing traces of toxic metals (Alloway, 2013).

## 3.5. Impact on Growth and Commercial Quality

The average fruit weight drops from 180 g to 110 g, suggesting slowed growth under environmental stress (Zhang et al., 2014; Dzokom, 2025). Vegetable firmness drastically decreases (3.2 N vs. 6.5 N), affecting shelf life and commercial appeal (Kader, 2002; Dzokom et al., 2024a,b; Dzokom, 2023). The deformation rate reaches 18.7%, well above the 5% threshold
tolerated in the commercial market (OECD,
2017).

<table><caption>Table 4: Glyphosate and Nitrate Residues</caption>
  <thead>
    <tr>
      <th>Parameter</th>
      <th>Tomatoes (Wells)</th>
      <th>Tomatoes (Reservoirs)</th>
      <th>Lettuces (Wells)</th>
      <th>Lettuces (Reservoirs)</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Glyphosate (µg/kg)</td>
      <td>0.8 ± 0.2</td>
      <td>5.6 ± 1.1</td>
      <td>1.2 ± 0.3</td>
      <td>8.9 ± 1.5</td>
    </tr>
    <tr>
      <td>Nitrates (mg/kg)</td>
      <td>45 ± 5</td>
      <td>112 ± 10</td>
      <td>80 ± 7</td>
      <td>205 ± 15</td>
    </tr>
  </tbody>
</table>

The values recorded in vegetables from the reservoirs exceed the limits set by the EU for human consumption (200 mg/kg for nitrates in lettuces). This excessive accumulation can be attributed to the alteration of nitrogen metabolism in plants due to chronic exposure to glyphosates (Duke & Powles, 2008; Dzokom, 2025; Dzokom, 2023).

**3.8. Alteration of Nutritional Value**

Analyses show a reduction in vitamin and
mineral content in fruits and vegetables
irrigated with reservoir water:

* Vitamin C (mg/100g):

o Tomatoes (Wells): 24.5 ± 2.3

o Tomatoes (Reservoirs): 15.2 ± 1.7

* Calcium (mg/kg):

o Lettuces (Wells): 550 ± 30

o Lettuces (Reservoirs): 370 ± 25

According to Zobiole et al. (2010), crop exposure to glyphosate reduces their ability to absorb essential nutrients by disrupting soil enzymatic activity and mycorrhizal symbiosis, which explains the decrease in their nutritional value.

4. General Discussion and
Recommendations

The results confirm that reservoir waters,
exposed to agricultural pollution, exhibit
lower quality compared to wells, affecting
not only aquatic biodiversity but also
agricultural production quality.

**Environmental and Health Implications**

Surface water contamination by
glyphosates and nitrates increases the risk

of eutrophication, reducing aquatic
biodiversity and compromising local
ecosystem sustainability. The accumulation
of pesticide residues in vegetables poses a
health risk, particularly due to the potential
effects of glyphosates on human health
(endocrine disruption, renal toxicity)
(Mesnage et al., 2015).

Recommendations for Sustainable
Management

1. Encouraging Alternative Agricultural Techniques

o Promote the use of biological alternatives to glyphosates (plant extracts, mechanical tillage, agroforestry).

o Advocate agroecology and
crop rotation to reduce
dependence on chemical
inputs.

o Establish vegetative buffer
strips around agricultural
plots to filter pollutants
before they reach water
bodies.

2. Improving Irrigation Water Management

o Raise awareness among farmers about the importance of rational irrigation and protecting water sources.

o Encourage the construction of protected wells and the implementation of filtration systems to ensure better water quality.
* Introduce phytoremediation techniques (using aquatic plants to filter contaminants).

### 3. Monitoring and Regulating Water and Agricultural Production Quality

* Establish regular monitoring of pesticide and nitrate levels in surface and groundwater.

* Implement strict controls on agricultural products intended for consumption, ensuring compliance with permissible residue thresholds.

* Strengthen local laboratory capacities for regular water and food quality analysis.

### 4. Raising Awareness and Engaging Local Stakeholders

* Involve farmer organizations, local institutions, and researchers in implementing strategies adapted to the Mayo-Tsanaga realities.

* Organize training on good agricultural practices and sustainable water resource management.

* Promote incentive public policies to encourage farmers to adopt environmentally friendly practices.

## Perspectives

Further research could deepen the understanding of glyphosate's impact on human health in this specific region and assess the effectiveness of alternative techniques to restore water quality and biodiversity. An integrated approach combining environmental sciences, agronomy, and public policy is essential to ensure sustainable agricultural development and protect Mayo-Tsanaga's natural

resources. In conclusion, a rational and preventive water resource management strategy is imperative to guarantee ecological sustainability and food security in the Sahelian zone.

## Conclusion and Recommendations

The comparative study of irrigation water quality from wells and glyphosate-contaminated reservoirs in Mayo-Tsanaga has highlighted notable disparities between these two water sources. The results show that:

1. Reservoir waters exhibit higher contamination with glyphosates and nitrates than well waters, due to pesticide and fertilizer runoff from surrounding agricultural fields. These concentrations exceed WHO-defined drinking water quality standards, posing significant environmental and health risks.

2. The impact on aquatic biodiversity is concerning, with a reduction in macroinvertebrate diversity and a proliferation of cyanobacteria in reservoirs, indicating advanced eutrophication. This water quality degradation affects local ecosystems and could disrupt the food chain.

3. Fruits and vegetables irrigated with reservoir waters contain high levels of glyphosate and nitrate residues, altering their nutritional value and potentially compromising their safety for human consumption. The bioaccumulation of these contaminants in the food chain could have long-term adverse health effects on local populations.

4. Irrigation wells represent a safer alternative, although their quality also depends on local water resource management and the proximity of pollution sources.
Thus, this study highlights the need for rigorous management of agricultural practices to limit herbicide impacts on water resources and agricultural production.

## Recommendations

To mitigate the observed negative effects and ensure sustainable water and biodiversity management, several measures should be implemented:

1. **Reducing Herbicide Use and Adopting Sustainable Agricultural Practices**

o Encourage the use of biological alternatives to glyphosates (plant extracts, mechanical tillage, agroforestry).

o Promote agroecology and crop rotation to limit dependency on chemical inputs.

o Establish vegetative buffer strips around agricultural plots to filter pollutants before they reach water bodies.

2. **Improving Irrigation Water Management**

o Educate farmers on the importance of rational irrigation and water source protection.

o Encourage the construction of protected wells and the implementation of filtration systems for better water quality.

o Introduce phytoremediation techniques (using aquatic plants to filter contaminants).

3. **Monitoring and Regulating Water and Agricultural Production Quality**

o Establish regular monitoring of pesticide and nitrate

levels in surface and groundwater.

o Enforce strict controls on agricultural products for consumption, ensuring compliance with permissible residue thresholds.

o Strengthen local laboratory capacities for regular water and food quality analysis.

4. **Raising Awareness and Engaging Local Stakeholders**

o Involve farmer organizations, local institutions, and researchers in implementing strategies adapted to the Mayo-Tsanaga context.

o Organize training on good agricultural practices and sustainable water resource management.

o Promote incentive public policies to encourage farmers to adopt environmentally friendly practices.

## Future Research Directions

Additional research could further explore the impact of glyphosates on human health in this specific region and evaluate the effectiveness of alternative techniques to restore water quality and biodiversity. An integrated approach combining environmental sciences, agronomy, and public policy is essential to ensure sustainable agricultural development and protect Mayo-Tsanaga's natural resources. In conclusion, a rational and preventive approach to water resource management is crucial to ensuring ecological sustainability and food security in the Sahelian zone.

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